A POLICY on GEOMETRIC DESIGN: AASHTO GUIDE
•
22 likes•5,713 views
This document provides a summary of a policy document on geometric design of highways and streets published in 2001 by the American Association of State Highway and Transportation Officials (AASHTO). It includes lists of the executive committee and task force members for 2000-2001. The document contains technical specifications and guidelines for highway design.
Recommended
More Related Content
What's hot
What's hot (20)
Viewers also liked
Viewers also liked (20)
Similar to A POLICY on GEOMETRIC DESIGN: AASHTO GUIDE
Similar to A POLICY on GEOMETRIC DESIGN: AASHTO GUIDE (20)
Recently uploaded
Recently uploaded (20)
A POLICY on GEOMETRIC DESIGN: AASHTO GUIDE
- 2. A POLICY on GEOMETRIC DESIGN of HIGHWAYS and STREETS 2001 American Association of State Highway and Transportation Officials 444 North Capitol Street, N.W., Suite 249 Washington, D.C. 20001 (202) 624-5800 www.transportation.org © Copyright 2001, by the American Association of State Highway and Transportation Officials. All Rights Reserved. This book, or parts thereof, may not be reproduced in any form without written permission of the publisher. Printed in the United States of America. ISBN: 1-56051-156-7
- 3. ii American Association of State Highway and Transportation Officials Executive Committee 2000-2001 President: Thomas R. Warne, Utah Vice President: Dean Carlson, Kansas Secretary/Treasurer: Larry King, Pennsylvania AASHTO Executive Director: John Horsley, Washington, D.C. Immediate Past President: Dan Flowers, Arkansas Regional Representatives Region I: (NASTO) William Ankner, Rhode Island—President Joseph Boardman, New York—Vice President Region II: (SASHTO) David McCoy, North Carolina—President Bruce Saltsman, Tennessee—Vice President Region III: (Mississippi Valley) Cristine Klika, Indiana—President Kirk Brown, Illinois—Vice President Region IV: (WASHTO) Joseph Perkins, Alaska—President Neal McCaleb, Oklahoma—Vice President
- 4. iii Task Force on Geometric Design 2000 Members Terry L. Abbott California 1999 – 2000 Don T. Arkle Alabama 1991 – Present Ray Ballentine Mississippi 1997 – 1999 Harold E. Bastin National League of Cities 1993 – 1999 Paul Bercich Wyoming 1995 – Present James O. Brewer Kansas 1986 – Present Jerry Champa California 1997 – 1999 Philip J. Clark New York 1992 – Present Susan Davis Oklahoma 1994 – 1995 Alan Glenn California 1992 – 1997 Charles A. Goessel New Jersey 1986 – Present Dennis A. Grylicki National Association of County Engineers 1992 – 1999 Irving Harris Mississippi 1992 – 1997 David Hutchison National League of Cities 1999 – Present John LaPlante American Public Works Association 1989 – Present Ken Lazar Illinois 1990 – 2000 Donald A. Lyford New Hampshire 1992 – Present Mark A. Marek Texas l986 – Present Terry H. Otterness Arizona 1997 – Present Steven R. Oxoby Nevada 1993 – Present Robert P. Parisi Port Authority of New York and New Jersey 1992 – Present Randy Peters Nebraska 1993 – 1998 John Pickering Mississippi 1999 – Present William A. Prosser FHWA, Secretary 1995 – Present Norman H. Roush West Virginia 1979 – Present Joe Ruffer National League of Cities 1999 – Present John Sacksteder Kentucky 1991 – 2000 Larry Sutherland Ohio 1991 – Present Charlie V. Trujillo New Mexico 1998 – Present Robert L. Walters Arkansas, Chairman 1982 – Present Ted Watson Nebraska 1998 – Present
- 5. iv AASHTO Highway Subcommittee on Design 2000-2001 Dr. Kam K. Movassaghi, LOUISIANA, Chair Susan Martinovich, NEVADA, Vice-Chair Dwight A. Horne, FHWA, Secretary — Ken F. Kobetsky, P.E., AASHTO, Staff Liaison ALABAMA— Arkle, Don T. Chief, Design Bureau Alabama Department of Transportation 1409 Coliseum Boulevard Montgomery, AL 36130-3050 ALABAMA— Walker, Steven E. Assistant Chief Design Engineer Alabama Department of Transportation 1409 Coliseum Boulevard Montgomery, AL 36130-3050 ALASKA— Hogins, Gary Chief of Design & Construction Standards Alaska Department of Transportation & Public Facilities 3132 Channel Drive Juneau, AK 99801-7898 ARIZONA— Louis, John L. Assistant State Engineer, Roadway Group Arizona Department of Transportation 205 South 17th Ave., Mail Drop 611E Phoenix, AZ 85007-3213 ARKANSAS— Loe, Dale F. Assistant Chief Engineer—Design Arkansas State Highway & Transportation Department P.O. Box 2261, 10324 Interstate 30 State Highway Building Little Rock, AR 72203-2261 ARKANSAS— McConnell,Phillip L. Engineer of Roadway Design Arkansas State Highway & Transportation Department P.O. Box 2261, 10324 Interstate 30 State Highway Building Little Rock, AR 72203-2261 CALIFORNIA— Buckley, Robert L. State and Local Project Development Program Manager California Department of Transportation P.O. Box 942874, 1120 N Street Sacramento, CA 94273 COLORADO— Harris, Timothy J. Project Development Branch Manager Colorado Department of Transportation 4201 East Arkansas Avenue, Room 406 Denver, CO 80222 CONNECTICUT— Bard, Carl F. Principal Engineer Connecticut Department of Transportation P.O. Box 317546/2800 Berlin Turnpike Newington, CT 06131-7546 CONNECTICUT— Byrnes, James F. Chief Engineer Connecticut Department of Transportation P.O. Box 317546/2800 Berlin Turnpike Newington, CT 06131-7546 CONNECTICUT— Smith, Bradley J. Manager of State Design Connecticut Department of Transportation P.O. Box 317546/2800 Berlin Turnpike Newington, CT 06131-7546 DELAWARE— Angelo, Michael A. Assistant Director, Design Support Delaware Department of Transportation P.O. Box 778, Bay Road, Route 113 Dover, DE 19903-0778 DELAWARE— Canning, Kevin Supervising Engineer—Road Design Delaware Department of Transportation P.O. Box 778, Bay Road, Route 113 Dover, DE 19903-0778 DELAWARE— Satterfield, Joe Specifications Engineer Delaware Department of Transportation P.O. Box 778, Bay Road, Route 113 Dover, DE 19903-0778 DELAWARE— Simmons, Michael H. Road Design Engineer Delaware Department of Transportation P.O. Box 778, Bay Road, Route 113 Dover, DE 19903-0778 FLORIDA— Hattaway, Billy L. State Roadway Design Engineer Florida Department of Transportation 605 Suwannee Street Tallahassee, FL 32399-0450 FLORIDA— Mills, Jim Roadway Design Engineer Florida Department of Transportation 605 Suwannee Street Tallahassee, FL 32399-0450 FLORIDA— Simmons, Freddie L. State Highway Engineer Florida Department of Transportation 605 Suwannee Street, MS 38 Tallahassee, FL 32311-0450 GEORGIA— Kennerly, James State Road and Airport Design Engineer Georgia Department of Transportation 2 Capitol Square, Room 444 Atlanta, GA 30334
- 6. v GEORGIA— Palladi, Joseph State Urban and Multi-Modal Design Engineer Georgia Department of Transportation No. 2 Capitol Square, Room 356 Atlanta, GA 30334 GEORGIA— Scott,WalkerW. Georgia Department of Transportation 2 Capitol Square Atlanta, GA 30334 HAWAII— Abe, Casey Engineer Program Manager, Design Branch, Highways Division Hawaii Department of Transportation 601 Kamokila Boulevard, Room 688A Kapolei, HI 96707 HAWAII— Fronda, Julius Highway Design Section Head Hawaii Department of Transportation 601 Kapolei Boulevard, Room 609 Kapolei, HI 96707 IDAHO— Hutchinson, Steven C. Assistant Chief Engineer—Development Idaho Transportation Department P.O. Box 7129, 3311 W. State Street Boise, ID 83707 IDAHO— Laragan, Gregory Roadway Design Engineer Idaho Transportation Department P.O. Box 7129, 3311 W. State Street Boise, ID 83707 ILLINOIS— Hine, Michael Chief of Design and Environment Illinois Department of Transportation 2300 S. Dirksen Parkway Springfield, IL 62764 ILLINOIS— Seyfried, Robert Northwestern University Center for Public Safety 405 Church Street Evanston, IL 60204 INDIANA— Klika, Phelps H. Director, Division of Design Indiana Department of Transportation 100 N. Senate Avenue Indianapolis, IN 46204-2217 IOWA— Dillavou, Mitch Director, Office of Design Iowa Department of Transportation 800 Lincoln Way Ames, IA 50010 IOWA— Little, David Deputy Director Iowa Department of Transportation, Engineering Division 800 Lincoln Way Ames, IA 50010 KANSAS— Adams, Richard G. Road Design Engineer Kansas Department of Transportation 915 Harrison Ave., 9th Floor Topeka, KS 66612-1568 KANSAS— Brewer, James O. Engineering Manager—State Road Office Kansas Department of Transportation Docking State Office Building, 9th Floor Topeka, KS 66612-1568 KENTUCKY— Kratt, David Location Branch Manager Kentucky Transportation Cabinet, Division Of Highway Design High and Clinton streets, 6th Floor Frankfort,KY 40622 KENTUCKY— Sperry, Kenneth R. Assistant State Highway Engineer Kentucky Transportation Cabinet, State Highway Engineer's Office 501 High Street, State Office Building Frankfort,KY 40622 LOUISIANA— Israel, N. Kent Roadway Design Engineer Administrator Louisiana Department of Transportation and Development P.O. Box 94245, 1201 Capitol Access Road Baton Rouge, LA 70804-9245 LOUISIANA— Kalivoda, Nicholas Traffic and Geometrics Design Engineer Louisiana Department of Transportation and Development Trenton, LA 86250 LOUISIANA— Porta, Lloyd E. Design Squad Louisiana Department of Transportation and Development P.O. Box 94245, 1201 Capitol Access Road Baton Rouge, LA 70804-9245 MAINE— Casey, Jerry A. Program Manager—Urban and Arterial Highways Maine Department of Transportation Transportation Building, State House Station 16 Augusta, ME 04333-0016 MARYLAND— Douglass, Robert D. Deputy Chief Engineer-Highway Development Maryland Department of Transportation, State Highway Administration 707 N. Calvert Street, Mail Stop C102 Baltimore, MD 21202 MARYLAND— McClelland, Kirk G. Highway Design Division Chief Maryland Department of Transportation, State Highway Administration 707 N. Calvert Street Baltimore, MD 21202 MASSACHUSETTS— Blundo, John Deputy Chief Engineer, Highway Engineering Massachusetts Highway Department 10 Park Plaza, Room 6340 Boston, MA 02116-3973 MASSACHUSETTS— Wood, Stanley Highway Location and Design Engineer Massachusetts Highway Department 10 Park Plaza Boston, MA 02116 MICHIGAN— Miller, Paul F. Engineer of Design Michigan Department of Transportation, Design Division State Transportation Building 425 W. Ottawa Street, P.O. Box 30050 Lansing, MI 48909
- 7. vi MINNESOTA— Gerdes, Delbert Director, Technical Support Minnesota Department of Transportation Transportation Building, MS 675, 395 John Ireland Boulevard St. Paul, MN 55155-1899 MISSISSIPPI— Pickering, John B. Roadway Design Engineer Mississippi Department of Transportation P.O. Box 1850, 401 North West Street Jackson, MS 39215-1850 MISSISSIPPI— Ruff, Wendel T. Assistant Chief Engineer—Preconstruction Mississippi Department of Transportation P.O. Box 1850, 401 North West Street Jackson, MS 39215-1850 MISSOURI— Nichols, David B. Director of Project Development Missouri Department of Transportation P.O. Box 270 Jefferson City, MO 65102-0207 MISSOURI— Yarnell,William (Bill) Division Engineer Design Missouri Department of Transportation 105 West Capitol Avenue, P.O. Box 270 Jefferson City, MO 65102-0207 MONTANA— Peil, Carl S. Preconstruction Engineer Montana Department of Transportation P.O. Box 201001, 2701 Prospect Avenue Helena, MT 59620-1001 NEBRASKA— Poppe, Eldon D. Engineer, Roadway Design Division Nebraska Department of Roads 1500 Nebraska Highway 2 P.O. Box 94759 Lincoln, NE 68509-4759 NEVADA— Oxoby, Steve R. Chief Road Design Engineer Nevada Department of Transportation 1263 S. Stewart Street Carson City, NV 89712 NEW HAMPSHIRE— Green, Craig A. Administrator, Bureau of Highway Design New Hampshire Department of Transportation John O. Morton Building, P.O. Box 483 1 Hazen Drive Concord, NH 03301-0483 NEW JERSEY— Dunne, RichardW. Director, Design Services New Jersey Department of Transportation 1035 Parkway Avenue, CN 600 Trenton, NJ 08625-0600 NEW JERSEY— Eisdorfer, Arthur J. Manager, Bureau of Civil Engineering New Jersey Department of Transportation 1035 Parkway Avenue, CN 600 Trenton, NJ 08625-0600 NEW JERSEY— Miller, Charles Executive Assistant, Office of the Director New Jersey Department of Transportation, Division Of Design Services 1035 Parkway Avenue, CN 600 Trenton, NJ 08625-0600 NEW MEXICO— Maestas, Roy Chief, Internal Design Bureau New Mexico State Highway and Transportation Department P.O. Box 1149, 1120 Cerrillos Road Santa Fe, NM 87504-1149 NEW MEXICO— Trujillo, Charlie V. Deputy Secretary of Transportation Planning and Design New Mexico State Highway and Transportation Department P.O. Box 1149, 1120 Cerrillos Road Santa Fe, NM 87504-1149 NEW YORK— Bellair,Peter J. Director of Design Quality Insurance Bureau New York Department of Transportation Building 5, State Office Campus 1220 Washington Avenue Albany, NY 12232-0750 NEW YORK— Clark, Phillip J. Deputy Chief Engineer/Director, Design Division New York Department of Transportation Building 5, State Office Campus 1220 Washington Avenue Albany, NY 12232-0748 NEW YORK— D'Angelo , Daniel Director, Design Quality Assurance Bureau New York Department of Transportation 1220 Washington Ave. Building 5, Room 410 Albany, NY 12232-0751 NORTH CAROLINA— Alford, John E. State Roadway Design Unit North Carolina Department of Transportation P.O. Box 25201, 1 South Wilmington Street Raleigh, NC 27611-5201 NORTH CAROLINA— Barbour, Deborah M. State Design Engineer North Carolina Department of Transportation P.O. Box 25201, 1 South Wilmington Street Raleigh, NC 27611-5201 NORTH CAROLINA— Hill, Len Deputy Administrator, Pre-Construction North Carolina Department of Transportation P.O. Box 25201, 1 South Wilmington Street Raleigh, NC 27611-5201 NORTH CAROLINA— Morton, Don R. Deputy Administrator—Preconstruction North Carolina Department of Transportation, Division of Highways P.O. Box 25201, 1 South Wilmington Street Raleigh, NC 27611-5201 NORTH DAKOTA— Birst, Kenneth E. Design Engineer North Dakota Department of Transportation 608 E. Boulevard Avenue Bismarck, ND 58505-0700 OHIO— Misel, Cash Assistant Director and Chief Engineer Ohio Department of Transportation, Planning and Production Management 1980 West Broad Street Columbus, OH 43223-1102
- 8. vii OHIO— Sutherland, Larry F. Deputy Director, Office of Roadway Engineering Services Ohio Department of Transportation 1980 West Broad Street Columbus, OH 43223 OKLAHOMA— Senkowski, Christine M. Division Engineer, Roadway Design Oklahoma Department of Transportation 200 N. E. 21st Street, Room 2c-2 Oklahoma City, OK 73105-3204 OKLAHOMA— Taylor, Bruce E. Chief Engineer Oklahoma Department of Transportation 200 N.E. 21st Street Oklahoma City, OK 73105-3204 OREGON— Greenberg, Dave Design Unit Manager Oregon Department of Transportation 355 Capitol Street N.E., Room 200 Salem, OR 97310 OREGON— Nelson, Catherine Manager, Roadway Engineering Section Oregon Department of Transportation 200 Transportation Building Salem, OR 97310 OREGON— Scheick, Jeff Manager, Technical Services Oregon Department of Transportation Transportation Building, 355 Capitol Street Salem, OR 97310 PENNSYLVANIA— Schreiber, Dean A. Chief, Highway Quality Assurance Div. Pennsylvania Department of Transportation P.O. Box 3161 Harrisburg, PA 17105-3161 PUERTO RICO— Hernandez Borges, Jose E. Director, Design Area Puerto Rico Highway and Transportation Authority P.O. Box 42007, Minillas Station San Juan, PR 00940-2007 RHODE ISLAND— Bennett, J. Michael Managing Engineer, Highway Design Rhode Island Department of Transportation State Office Building, 2 Capitol Hill Providence, RI 02903-1124 SOUTH CAROLINA— Kneece, Rocque L. C Fund Manager South Carolina Department of Transportation Silas N. Pearman Building, 955 Park Street Box 191 Columbia, SC 29202-0191 SOUTH CAROLINA— Pratt, Robert I. Project Development Engineer South Carolina Department of Transportation Silas N. Pearman Building, 955 Park Street Box 191 Columbia, SC 29202-0191 SOUTH CAROLINA— Walsh, John V. Program Development Engineer South Carolina Department of Transportation Silas N. Pearman Building, 955 Park Street Box 191 Columbia, SC 29202-0191 SOUTH DAKOTA— Bjorneberg,Timothy Chief Road Design Engineer South Dakota Department of Transportation 700 East Broadway Avenue Pierre, SD 57501-2586 SOUTH DAKOTA— Feller, Joe Chief Materials and Surfacing Engineer South Dakota Department of Transportation 700 East Broadway Avenue Pierre, SD 57501-2586 TENNESSEE— Jones, Jeff C. Civil Engineer Director, Design Division Tennessee Department of Transportation 505 Deaderick Street, Suite 700 Nashville,TN 37243-0339 TENNESSEE— Zeigler, James Director, Bureau of Planning and Development Tennessee Department of Transportation 700 James K. Polk Building, Fifth and Deaderick Nashville,TN 37243-0339 TEXAS— Wilson, Robert L. Director, Design Texas Department of Transportation 125 East 11th Street Austin, TX 78701-2483 UTAH— Mohanty, P. K. Roadway Design Engineer Utah Department of Transportation 4501 South 2700 West Salt Lake City, UT 84119 VERMONT— Lathrop, Donald H. Plan Support Engineer Vermont Agency of Transportation State Administration Building 133 State Street Montpelier, VT 05633-5001 VERMONT— Shattuck, Robert F. Roadway and Traffic Design Program Manager Vermont Agency of Transportation State Administration Building 133 State Street Montpelier, VT 05633-5001 VIRGINIA— Harris, James T. Assisant Division Administrator Virginia Department of Transportation, Location and Design Division 1401 E. Broad Street Richmond, VA 23219 VIRGINIA— Mills, Jimmy Location and Testing Engineer Virginia Department of Transportation 1401 East Broad Street Richmond, VA 23219 VIRGINIA— Mirshahi, Mohammad Assistant Division Administrator Virginia Department of Transportation 1401 E. Broad Street Richmond, VA 23219 WASHINGTON— Albin, Richard Standards Engineer Washington State Department of Transportation Transportation Building 310 Maple Park, P.O. Box 47329 Olympia, WA 98504-7329
- 9. viii WASHINGTON— Ziegler, Brian J. State Design Engineer Washington State Department of Transportation 505 Deaderick Street, Suite 700 Olympia, WA 98504-7300 WEST VIRGINIA— Clevenger, David E. Consultant Review Section Head West Virginia Department of Transportation, Engineering Division 1900 Kanawha Boulevard East, Building 5 Charleston, WV25305-0440 WEST VIRGINIA— Epperly, RandolphT. Deputy State Highway Engineer-Project Development West Virginia Department of Transportation 1900 Kanawha Boulevard East, Building 5 Charleston, WV25305-0440 WEST VIRGINIA— Roush, Norman H. Deputy Commissioner of Highways West Virginia Department of Transportation 1900 Kanawha Boulevard East, Building 5 Charleston, WV25305-0440 WISCONSIN— Haverberg, John E. Director, Bureau of Highway Development Wisconsin Department of Transportation P.O. Box 7910 4802 Sheboygan Avenue Madison, WI 53707-7910 WISCONSIN— Pfeiffer, Robert F. Project Development Chief Wisconsin Department of Transportation, District 2, Waukesha P.O. Box 7910 4802 Sheboygan Avenue Madison, WI 53707-7910 WYOMING— Bercich, Paul Project Development Engineer Wyoming Department of Transportation P.O. Box 1708, 5300 Bishop Boulevard Cheyenne, WY 82003-1708 DISTRICT OF COLUMBIA— Rice, John Manager, Engineering and Specifications Division Federal Aviation Administration 800 Independence Avenue, S.W. Room 616C, AAS-200 Washington, D.C. 20591-0001 DISTRICT OF COLUMBIA— Sandhu, Harbhajan S. Chief, Design and Engineering Division District of Columbia Department of Public Works 2000 14th Street, N.W., 5th Floor Washington, D.C. 20009 BRITISH COLUMBIA, CANADA— Voyer, Richard Senior Standards and Design Engineer British Columbia Ministry of Transportation and Highways 5B - 940 Blanshard Street Victoria, British Columbia V8W 3E6
- 10. ix Preface This Policy was developed as part of the continuing work of the Standing Committee on Highways. The Committee, then titled the Committee on Planning and Design Policies, was established in 1937 to formulate and recommend highway engineering policies. This Committee has developed A Policy on Geometric Design of Rural Highways, 1954 and 1965 editions; A Policy on Arterial Highways in Urban Areas, 1957; A Policy on Design of Urban Highways and Arterial Streets, 1973; Geometric Design Standards for Highways Other Than Freeways, 1969; A Policy on Geometric Design of Highways and Streets, 1984, 1990, and 1994; A Policy on Design Standards—Interstate System, 1956, 1967, and 1991; and a number of other AASHO and AASHTO policy and “guide” publications. An AASHTO publication is typically developed through the following steps: (1) The Committee selects subjects and broad outlines of material to be covered. (2) The appropriate subcommittee and its task forces, in this case, the Subcommittee on Design and its Task Force on Geometric Design, assemble and analyze relevant data and prepare a tentative draft. Working meetings are held and revised drafts are prepared, as necessary, and reviewed by the Subcommittee, until agreement is reached. (3) The manuscript is then submitted for approval by the Standing Committee on Highways and then the Executive Committee. Standards and policies must be adopted by a two-thirds vote by the Member Departments before publication. During the developmental process, comments are sought and considered from all the states, the Federal Highway Administration, and representatives of the American Public Works Association, the National Association of County Engineers, the National League of Cities, and other interested parties.
- 11. xi Table of Contents Preface ................................................................................................................................. ix Foreword............................................................................................................................. xv CHAPTER TITLES Chapter 1 Highway Functions.........................................................................................1 Chapter 2 Design Controls and Criteria .........................................................................15 Chapter 3 Elements of Design..................................................................................... 109 Chapter 4 Cross Section Elements............................................................................... 309 Chapter 5 Local Roads and Streets.............................................................................. 383 Chapter 6 Collector Roads and Streets......................................................................... 423 Chapter 7 Rural and Urban Arterials............................................................................ 447 Chapter 8 Freeways ................................................................................................... 507 Chapter 9 Intersections ............................................................................................... 559 Chapter 10 Grade Separations and Interchanges............................................................. 747 Chapter 1 HIGHWAY FUNCTIONS Page Systems and Classifications.....................................................................................................1 The Concept of Functional Classification .................................................................................1 Hierarchies of Movements and Components......................................................................1 Functional Relationships..................................................................................................4 Access Needs and Controls ..............................................................................................6 Functional System Characteristics............................................................................................7 Definitions of Urban and Rural Areas...............................................................................7 Functional Categories......................................................................................................8 Functional Systems for Rural Areas..................................................................................8 Rural Principal Arterial System.................................................................................8 Rural Minor Arterial System.....................................................................................9 Rural Collector System.............................................................................................9 Rural Local Road System.........................................................................................9 Extent of Rural Systems ......................................................................................... 10 Functional Highway Systems in Urbanized Areas ........................................................... 10 Urban Principal Arterial System..............................................................................10 Urban Minor Arterial Street System........................................................................11 Urban Collector Street System................................................................................12 Urban Local Street System.....................................................................................12 Length of Roadway and Travel on Urban Systems ...................................................12 Functional Classification as a Design Type ..................................................................... 13 References........................................................................................................................... 14
- 12. xii Chapter 2 DESIGN CONTROLS AND CRITERIA Introduction..........................................................................................................................15 Design Vehicles....................................................................................................................15 General Characteristics..................................................................................................15 Minimum Turning Paths of Design Vehicles...................................................................18 Vehicle Performance .....................................................................................................43 Vehicular Pollution........................................................................................................43 Driver Performance..............................................................................................................46 Introduction..................................................................................................................46 Older Drivers................................................................................................................47 The Driving Task..........................................................................................................47 The Guidance Task.......................................................................................................48 Lane Placement and Road Following.......................................................................48 Car Following........................................................................................................48 Passing Maneuvers.................................................................................................49 Other Guidance Activities.......................................................................................49 The Information System.................................................................................................49 Traffic Control Devices..........................................................................................49 The Roadway and its Environment..........................................................................49 Information Handling.....................................................................................................50 Reaction Time........................................................................................................50 Primacy.................................................................................................................53 Expectancy............................................................................................................53 Driver Error ..................................................................................................................53 Errors Due to Driver Deficiencies ...........................................................................54 Errors Due to Situation Demands ............................................................................56 Speed and Design..........................................................................................................56 Design Assessment........................................................................................................57 Traffic Characteristics....................................................................................................58 General Considerations...........................................................................................58 Volume.........................................................................................................................58 Average Daily Traffic.............................................................................................58 Peak-Hour Traffic ..................................................................................................59 Directional Distribution.................................................................................................62 Composition of Traffic ..................................................................................................63 Projection of Future Traffic Demands.............................................................................65 Speed...........................................................................................................................66 Operating Speed.....................................................................................................66 Running Speed.......................................................................................................67 Design Speed.........................................................................................................67 Traffic Flow Relationships .............................................................................................72 Highway Capacity ................................................................................................................74 General Characteristics..................................................................................................74 Application ...................................................................................................................74
- 13. xiii Capacity as a Design Control..........................................................................................75 Design Service Flow Rate Versus Design Volume....................................................75 Measures of Congestion..........................................................................................75 Relation Between Congestion and Traffic Flow Rate................................................76 Acceptable Degrees of Congestion ..........................................................................77 Principles for Acceptable Degrees of Congestion......................................................78 Reconciliation of Principles for Acceptable Degrees of Congestion ...........................80 Factors Other Than Traffic Volume That Affect Operating Conditions..............................81 Highway Factors....................................................................................................81 Alignment..............................................................................................................82 Weaving Sections...................................................................................................82 Ramp Terminals.....................................................................................................82 Traffic Factors.......................................................................................................83 Peak Hour Factor ...................................................................................................83 Levels of Service...........................................................................................................84 Design Service Flow Rates ............................................................................................85 Weaving Sections...................................................................................................85 Multilane Highways Without Access Control...........................................................86 Arterial Streets and Urban Highways.......................................................................86 Intersections...........................................................................................................88 Pedestrians and Bicycles.........................................................................................88 Access Control and Access Management ...............................................................................88 General Conditions........................................................................................................88 Basic Principles of Access Management.........................................................................90 Access Classifications....................................................................................................90 Methods of Controlling Access......................................................................................91 Benefits of Controlling Access.......................................................................................91 The Pedestrian......................................................................................................................96 General Considerations ..................................................................................................96 General Characteristics..................................................................................................96 Walking Speeds ............................................................................................................97 Walkway Capacities......................................................................................................98 Sidewalks ..............................................................................................................98 Intersections...........................................................................................................99 Reducing Pedestrian-Vehicular Conflicts.................................................................99 Characteristics of Persons With Disabilities ....................................................................99 Mobility Impairments...........................................................................................100 Visual Impairments..............................................................................................100 Developmental Impairments .................................................................................100 Bicycle Facilities................................................................................................................ 100 Safety................................................................................................................................ 101 Environment....................................................................................................................... 106 Economic Analysis ............................................................................................................. 106 References......................................................................................................................... 106
- 14. xiv Chapter 3 ELEMENTS OF DESIGN Introduction........................................................................................................................ 109 Sight Distance.................................................................................................................... 109 General Considerations ................................................................................................ 109 Stopping Sight Distance............................................................................................... 110 Brake Reaction Time............................................................................................110 Braking Distance .................................................................................................111 Design Values......................................................................................................113 Effect of Grade on Stopping..................................................................................113 Variation for Trucks .............................................................................................114 Decision Sight Distance............................................................................................... 115 Passing Sight Distance for Two-Lane Highways............................................................ 118 Criteria for Design................................................................................................118 Design Values......................................................................................................122 Effect of Grade on Passing Sight Distance.............................................................125 Frequency and Length of Passing Sections.............................................................125 Sight Distance for Multilane Highways......................................................................... 126 Criteria for Measuring Sight Distance........................................................................... 127 Height of Driver’s Eye .........................................................................................127 Height of Object..................................................................................................127 Sight Obstructions................................................................................................128 Measuring and Recording Sight Distance on Plans .................................................128 Horizontal Alignment.......................................................................................................... 131 Theoretical Considerations........................................................................................... 131 General Considerations ................................................................................................ 132 Superelevation .....................................................................................................132 Side Friction Factor..............................................................................................133 Distribution of e and f Over a Range of Curves......................................................138 Design Considerations ................................................................................................. 141 Maximum Superelevation Rates............................................................................141 Minimum Radius..................................................................................................142 Design for Rural Highways, Urban Freeways, and High-Speed Urban Streets..........143 Procedure for Development of Finalized e Distribution...........................................146 Design Superelevation Tables...............................................................................155 Sharpest Curve Without Superelevation.................................................................166 Effects of Grades.................................................................................................167 Transition Design Controls........................................................................................... 168 General Considerations.........................................................................................168 Tangent-to-Curve Transition.................................................................................169 Spiral Curve Transitions .......................................................................................176 Length of Spiral...................................................................................................177 Compound Curve Transition.................................................................................184 Methods of Attaining Superelevation.....................................................................184 Design of Smooth Profiles for Traveled Way Edges...............................................187
- 15. xv Axis of Rotation with a Median.............................................................................188 Minimum Transition Grades.................................................................................190 Turning Roadway Design............................................................................................. 191 Design for Low-Speed Urban Streets............................................................................ 192 Maximum Comfortable Speed on Horizontal Curves..............................................195 Minimum Superelevation Runoff Length...............................................................195 Minimum Radii and Minimum Lengths of Superelevation Runoff for Limiting Values of e and f ....................................................................................198 Curvature of Turning Roadways and Curvature at Intersections...................................... 198 Minimum Radius for Turning Speed......................................................................198 Transitions and Compound Curves........................................................................203 Length of Spiral...................................................................................................203 Compound Circular Curves ..................................................................................205 Offtracking.................................................................................................................. 206 Derivation of Design Values for Widening on Horizontal Curves............................206 Traveled Way Widening on Horizontal Curves.............................................................. 212 Design Values for Traveled Way Widening............................................................214 Application of Widening on Curves.......................................................................218 Widths for Turning Roadways at Intersections............................................................... 220 Design Values......................................................................................................223 Widths Outside Traveled Way..............................................................................226 Sight Distance on Horizontal Curves ............................................................................ 228 Stopping Sight Distance .......................................................................................228 Passing Sight Distance .........................................................................................232 General Controls for Horizontal Alignment................................................................... 233 Vertical Alignment ............................................................................................................. 235 Terrain........................................................................................................................ 235 Grades........................................................................................................................ 235 Vehicle Operating Characteristics on Grades .........................................................236 Control Grades for Design ....................................................................................239 Critical Lengths of Grade for Design.....................................................................242 Climbing Lanes........................................................................................................... 247 Climbing Lanes for Two-Lane Highways ..............................................................247 Climbing Lanes on Freeways and Multilane Highways...........................................251 Methods for Increasing Passing Opportunities on Two-Lane Roads............................... 254 Passing Lanes......................................................................................................254 Turnouts..............................................................................................................257 Shoulder Driving..................................................................................................258 Shoulder Use Sections ..........................................................................................259 Emergency Escape Ramps ........................................................................................... 259 General................................................................................................................259 Need and Location for Emergency Escape Ramps..................................................261 Types of Emergency Escape Ramps ......................................................................262 Design Considerations..........................................................................................264 Brake Check Areas ..............................................................................................268 Maintenance........................................................................................................268
- 16. xvi Vertical Curves........................................................................................................... 269 General Considerations.........................................................................................269 Crest Vertical Curves...........................................................................................270 Sag Vertical Curves .............................................................................................276 Sight Distance at Undercrossings ..........................................................................280 General Controls for Vertical Alignment................................................................282 Combinations of Horizontal and Vertical Alignment............................................................. 283 General Considerations ................................................................................................ 283 General Design Controls .............................................................................................. 284 Alignment Coordination in Design................................................................................ 285 Other Elements Affecting Geometric Design........................................................................ 286 Drainage..................................................................................................................... 286 Erosion Control and Landscape Development................................................................ 292 Rest Areas, Information Centers, and Scenic Overlooks ................................................. 293 Lighting...................................................................................................................... 294 Utilities....................................................................................................................... 296 General................................................................................................................296 Urban..................................................................................................................297 Rural...................................................................................................................298 Traffic Control Devices ............................................................................................... 298 Signing and Marking............................................................................................298 Traffic Signals .....................................................................................................299 Noise Barriers............................................................................................................. 300 Fencing....................................................................................................................... 301 Maintenance of Traffic Through Construction Areas..................................................... 301 References......................................................................................................................... 303 Chapter 4 CROSS SECTION ELEMENTS General.............................................................................................................................. 309 Pavement........................................................................................................................... 309 Surface Type............................................................................................................... 309 Cross Slope................................................................................................................. 309 Skid Resistance........................................................................................................... 314 Lane Widths....................................................................................................................... 315 Shoulders........................................................................................................................... 316 General Characteristics................................................................................................ 316 Width of Shoulders...................................................................................................... 318 Shoulder Cross Sections............................................................................................... 319 Shoulder Stability........................................................................................................ 321 Shoulder Contrast........................................................................................................ 322 Turnouts ..................................................................................................................... 322 Horizontal Clearance to Obstructions ................................................................................... 322 Curbs................................................................................................................................. 323 General Considerations ................................................................................................ 323
- 17. xvii Curb Configurations .................................................................................................... 324 Curb Placement........................................................................................................... 326 Drainage Channels and Sideslopes....................................................................................... 327 General Considerations ................................................................................................ 327 Drainage Channels ...................................................................................................... 327 Sideslopes................................................................................................................... 330 Illustrative Outer Cross Sections.......................................................................................... 333 Normal Crown Sections ............................................................................................... 333 Superelevated Sections ................................................................................................ 334 Traffic Barriers................................................................................................................... 335 General Considerations ................................................................................................ 335 Longitudinal Barriers................................................................................................... 337 Roadside Barriers.................................................................................................337 Median Barriers...................................................................................................338 Bridge Railings ........................................................................................................... 339 Crash Cushions ........................................................................................................... 340 Medians ............................................................................................................................. 341 Frontage Roads .................................................................................................................. 343 Outer Separations ............................................................................................................... 346 Noise Control..................................................................................................................... 348 General Considerations ................................................................................................ 348 General Design Procedures.......................................................................................... 349 Noise Reduction Designs ............................................................................................. 350 Roadside Control................................................................................................................ 352 General Considerations ................................................................................................ 352 Driveways .................................................................................................................. 352 Mailboxes................................................................................................................... 354 Tunnels.............................................................................................................................. 355 General Considerations ................................................................................................ 355 Types of Tunnels......................................................................................................... 356 General Design Considerations..................................................................................... 357 Tunnel Sections........................................................................................................... 357 Examples of Tunnels ................................................................................................... 359 Pedestrian Facilities............................................................................................................ 361 Sidewalks ................................................................................................................... 361 Grade-Separated Pedestrian Crossings .......................................................................... 363 Sidewalk Curb Ramps ................................................................................................. 365 Bicycle Facilities................................................................................................................ 371 Bus Turnouts...................................................................................................................... 372 Freeways .................................................................................................................... 372 Arterials...................................................................................................................... 372 Park-and-Ride Facilities............................................................................................... 374 Location ..............................................................................................................374 Design.................................................................................................................375 On-Street Parking ............................................................................................................... 377 References......................................................................................................................... 380
- 18. xviii Chapter 5 LOCAL ROADS AND STREETS Introduction........................................................................................................................ 383 Local Rural Roads .............................................................................................................. 384 General Design Considerations..................................................................................... 384 Design Traffic Volume .........................................................................................384 Design Speed.......................................................................................................384 Sight Distance......................................................................................................384 Grades.................................................................................................................386 Alignment............................................................................................................386 Cross Slope..........................................................................................................387 Superelevation .....................................................................................................387 Number of Lanes.................................................................................................387 Width of Traveled Way, Shoulder, and Roadway...................................................387 Structures............................................................................................................389 Bridges to Remain in Place...................................................................................389 Vertical Clearance ...............................................................................................389 Right-of-Way Width.............................................................................................391 Foreslopes ...........................................................................................................391 Horizontal Clearance to Obstructions.....................................................................391 Curbs ..................................................................................................................392 Intersection Design...............................................................................................392 Railroad Highway Grade Crossings.......................................................................392 Traffic Control Devices........................................................................................393 Bicycle Facilities..................................................................................................393 Erosion Control....................................................................................................393 Local Urban Streets ............................................................................................................ 393 General Design Considerations..................................................................................... 393 Design Traffic Volume .........................................................................................394 Design Speed.......................................................................................................394 Sight Distance......................................................................................................395 Grades.................................................................................................................395 Alignment............................................................................................................395 Cross Slope..........................................................................................................396 Superelevation .....................................................................................................396 Number of Lanes.................................................................................................396 Width of Roadway...............................................................................................397 Parking Lanes......................................................................................................397 Median................................................................................................................397 Curbs ..................................................................................................................398 Drainage..............................................................................................................398 Cul-De-Sacs and Turnarounds...............................................................................398 Alleys..................................................................................................................400 Sidewalks ............................................................................................................400 Sidewalk Curb Ramps ..........................................................................................402
- 19. xix Driveways ...........................................................................................................402 Roadway Widths for Bridges ................................................................................403 Horizontal Clearance to Obstructions.....................................................................403 Vertical Clearance ...............................................................................................403 Border Area.........................................................................................................403 Right-of-Way Width.............................................................................................404 Provision for Utilities...........................................................................................404 Intersection Design...............................................................................................404 Railroad-Highway Grade Crossings.......................................................................405 Street and Roadway Lighting ................................................................................406 Levels .................................................................................................................407 Traffic Control Devices........................................................................................407 Erosion Control....................................................................................................407 Landscaping.........................................................................................................407 Bicycle Facilities..................................................................................................408 Special-Purpose Roads........................................................................................................ 408 Introduction................................................................................................................ 408 Recreational Roads...................................................................................................... 408 General Considerations.........................................................................................408 Design Speed.......................................................................................................409 Design Vehicle.....................................................................................................410 Sight Distance......................................................................................................410 Passing Sight Distance .........................................................................................410 Grades.................................................................................................................411 Vertical Alignment...............................................................................................413 Horizontal Alignment...........................................................................................413 Number of Lanes.................................................................................................415 Widths of Traveled Way, Shoulder, and Roadway..................................................415 Cross Slope..........................................................................................................415 Clear Recovery Area............................................................................................417 Roadside Slopes...................................................................................................417 Roadside Barrier..................................................................................................417 Signing and Marking............................................................................................418 Structures............................................................................................................418 Resource Recovery Roads ........................................................................................... 418 Local Service Roads.................................................................................................... 420 References......................................................................................................................... 420 Chapter 6 COLLECTOR ROADS AND STREETS Introduction........................................................................................................................ 423 Rural Collectors.................................................................................................................. 424 General Design Considerations..................................................................................... 424 Design Traffic Volumes........................................................................................424 Design Speed.......................................................................................................424
- 20. xx Sight Distance......................................................................................................425 Grades.................................................................................................................425 Alignment............................................................................................................425 Cross Slope..........................................................................................................425 Superelevation .....................................................................................................428 Number of Lanes.................................................................................................428 Width of Roadway...............................................................................................428 Foreslopes ...........................................................................................................428 Structures............................................................................................................430 Bridges to Remain in Place...................................................................................430 Vertical Clearance ...............................................................................................431 Horizontal Clearance to Obstructions.....................................................................431 Right-of-Way Width.............................................................................................432 Intersection Design...............................................................................................432 Railroad-Highway Grade Crossings.......................................................................432 Traffic Control Devices........................................................................................433 Erosion Control....................................................................................................433 Urban Collectors ................................................................................................................ 433 General Design Considerations..................................................................................... 433 Design Traffic Volumes........................................................................................434 Design Speed.......................................................................................................434 Sight Distance......................................................................................................435 Grades.................................................................................................................435 Alignment............................................................................................................435 Cross Slope..........................................................................................................435 Superelevation .....................................................................................................435 Number of Lanes.................................................................................................437 Width of Roadway...............................................................................................437 Parking Lanes......................................................................................................437 Medians...............................................................................................................438 Curbs ..................................................................................................................439 Drainage..............................................................................................................439 Sidewalks ............................................................................................................440 Driveways ...........................................................................................................440 Roadway Widths for Bridges ................................................................................440 Vertical Clearance ...............................................................................................440 Horizontal Clearance to Obstructions.....................................................................441 Right-of-Way Width.............................................................................................441 Provision for Utilities...........................................................................................441 Border Area.........................................................................................................442 Intersection Design...............................................................................................442 Railroad-Highway Grade Crossings.......................................................................443 Street and Roadway Lighting ................................................................................443 Traffic Control Devices........................................................................................443 Erosion Control....................................................................................................444 Landscaping.........................................................................................................444
- 21. xxi References......................................................................................................................... 444 Chapter 7 RURAL AND URBAN ARTERIALS Introduction........................................................................................................................ 447 Rural Arterials.................................................................................................................... 447 General Characteristics................................................................................................ 447 General Design Considerations..................................................................................... 448 Design Speed.......................................................................................................448 Design Traffic Volume .........................................................................................448 Levels of Service .................................................................................................448 Sight Distance......................................................................................................449 Alignment............................................................................................................449 Grades.................................................................................................................450 Number of Lanes.................................................................................................450 Superelevation .....................................................................................................450 Cross Slope..........................................................................................................450 Vertical Clearances ..............................................................................................451 Structures............................................................................................................451 Traffic Control Devices........................................................................................451 Erosion Control....................................................................................................451 Widths.................................................................................................................452 Horizontal Clearance to Obstructions.....................................................................452 Cross Section and Right-of-Way...........................................................................453 Provision for Passing............................................................................................453 Ultimate Development of Four-Lane Divided Arterials...........................................454 Multilane Undivided Arterials ...................................................................................... 457 Divided Arterials......................................................................................................... 458 General Features..................................................................................................458 Lane Widths ........................................................................................................459 Cross Slope..........................................................................................................459 Shoulders ............................................................................................................459 Median Barrier Clearance.....................................................................................460 Medians...............................................................................................................460 Alignment and Profile ..........................................................................................461 Climbing Lanes on Multilane Arterials ..................................................................462 Superelevated Cross Sections................................................................................463 Cross Section and Right-of-Way Widths................................................................466 Sections With Widely Separated Roadways...........................................................469 Intersections.........................................................................................................470 Access Management.............................................................................................471 Bikeways and Pedestrian Facilities........................................................................471 Bus Turnouts .......................................................................................................472 Railroad-Highway Crossings.................................................................................472 Rest Areas...........................................................................................................472
- 22. xxii Urban Arterials................................................................................................................... 473 General Characteristics................................................................................................ 473 General Design Considerations..................................................................................... 474 Design Speed.......................................................................................................474 Design Traffic Volume .........................................................................................474 Levels of Service .................................................................................................474 Sight Distance......................................................................................................475 Alignment............................................................................................................475 Grades.................................................................................................................475 Superelevation .....................................................................................................475 Cross Slope..........................................................................................................476 Vertical Clearances ..............................................................................................476 Lane Widths ........................................................................................................476 Curbs and Shoulders.............................................................................................477 Number of Lanes.................................................................................................477 Width of Roadway...............................................................................................478 Medians...............................................................................................................478 Drainage..............................................................................................................482 Parking Lanes......................................................................................................482 Borders and Sidewalks .........................................................................................483 Railroad-Highway Crossings.................................................................................484 Roadway Width for Bridges..................................................................................485 Bridges to Remain in Place...................................................................................485 Horizontal Clearance to Obstructions.....................................................................485 Right-of-Way Width.............................................................................................486 Traffic Barriers....................................................................................................486 Access Management.................................................................................................... 486 General Features..................................................................................................486 Access Control by Statute .....................................................................................487 Access Control by Zoning.....................................................................................487 Access Control Through Driveway Regulations .....................................................487 Access Control Through Geometric Design............................................................488 Pedestrian Facilities..................................................................................................... 488 Provision for Utilities .................................................................................................. 490 Intersection Design...................................................................................................... 490 Operational Control and Regulations ............................................................................ 490 Traffic Control Devices........................................................................................490 Regulatory Measures............................................................................................492 Operational and Control Measures for Right-Turn Maneuvers.................................492 Operational and Control Measures for Left-Turn Maneuvers ..................................492 Regulation of Curb Parking...................................................................................495 Directional Lane Usage ........................................................................................495 Frontage Roads and Outer Separations.......................................................................... 498 Grade Separations and Interchanges ............................................................................. 498 Erosion Control........................................................................................................... 500 Lighting...................................................................................................................... 500
- 23. xxiii Bikeways.................................................................................................................... 500 Public Transit Facilities ............................................................................................... 500 Location of Bus Stops...........................................................................................501 Bus Turnouts .......................................................................................................504 Reserved Bus Lanes.............................................................................................504 Traffic Control Measures......................................................................................505 References......................................................................................................................... 506 Chapter 8 FREEWAYS Introduction........................................................................................................................ 507 General Design Considerations............................................................................................ 507 Design Speed.............................................................................................................. 507 Design Traffic Volumes............................................................................................... 508 Levels of Service......................................................................................................... 508 Pavement and Shoulders.............................................................................................. 508 Curbs.......................................................................................................................... 509 Superelevation............................................................................................................. 509 Grades........................................................................................................................ 509 Structures ................................................................................................................... 510 Vertical Clearance....................................................................................................... 510 Horizontal Clearance to Obstructions............................................................................ 511 Ramps and Terminals .................................................................................................. 512 Outer Separations, Borders, and Frontage Roads ........................................................... 512 Rural Freeways .................................................................................................................. 512 Alignment and Profile.................................................................................................. 513 Medians...................................................................................................................... 513 Sideslopes................................................................................................................... 516 Frontage Roads ........................................................................................................... 516 Urban Freeways ................................................................................................................. 517 General Design Characteristics..................................................................................... 517 Medians...................................................................................................................... 517 Depressed Freeways.................................................................................................... 517 General Characteristics.........................................................................................517 Slopes and Walls..................................................................................................518 Typical Cross Section...........................................................................................519 Restricted Cross Section .......................................................................................521 Walled Cross Section............................................................................................521 Examples of Depressed Freeways .........................................................................522 Elevated Freeways ...................................................................................................... 524 General Characteristics.........................................................................................524 Medians...............................................................................................................525 Ramps and Terminals ...........................................................................................525 Frontage Roads.................................................................................................... 526 Clearance to Building Line ................................................................................... 526
- 24. xxiv Typical Cross Section...........................................................................................526 Viaduct Freeways Without Ramps.........................................................................527 Two-Way Viaduct Freeways With Ramps .............................................................528 Freeways on Earth Embankment...........................................................................529 Examples of Elevated Freeways............................................................................530 Ground-Level Freeways .............................................................................................. 531 General Characteristics.........................................................................................531 Typical Cross Section...........................................................................................532 Restricted Cross Section .......................................................................................533 Example of a Ground-Level Freeway....................................................................534 Combination-Type Freeways ....................................................................................... 534 General Characteristics.........................................................................................534 Profile Control.....................................................................................................535 Cross-Section Control...........................................................................................537 Examples of Combination-Type Freeways.............................................................537 Special Freeway Designs ............................................................................................. 541 Reverse-Flow Roadways ......................................................................................541 Dual-Divided Freeways........................................................................................544 Freeways With Collector-Distributor Roads...........................................................547 Accommodation of Transit and High-Occupancy Vehicle Facilities............................... 547 General Considerations.........................................................................................547 Buses..................................................................................................................549 Rail Transit..........................................................................................................554 References......................................................................................................................... 558 Chapter 9 INTERSECTIONS Introduction........................................................................................................................ 559 General Design Considerations and Objectives..................................................................... 559 Types and Examples of Intersections.................................................................................... 562 General Considerations ................................................................................................ 562 Three-Leg Intersections ............................................................................................... 563 Basic Types of Intersections..................................................................................563 Channelized Three-Leg Intersections.....................................................................568 Four-Leg Intersections................................................................................................. 569 Basic Types.........................................................................................................569 Channelized Four-Leg Intersections ......................................................................570 Multileg Intersections .................................................................................................. 575 Modern Roundabouts................................................................................................... 578 Capacity Analysis ............................................................................................................... 583 Alignment and Profile ......................................................................................................... 583 General Considerations ................................................................................................ 583 Alignment................................................................................................................... 584 Profile......................................................................................................................... 586 Types of Turning Roadways................................................................................................ 587
- 25. xxv General....................................................................................................................... 587 Minimum Edge-of-Traveled-Way Designs.................................................................... 587 Design for Specific Conditions (Right-Angle Turns)...................................................... 596 Passenger Vehicles...............................................................................................597 Single-Unit Trucks and City Transit Buses ............................................................613 Semitrailer Combination Trucks............................................................................614 Oblique-Angle Turns............................................................................................614 Effect of Curb Radii on Turning Paths...................................................................615 Effect of Curb Radii on Pedestrians.......................................................................618 Corner Radii Into Local Urban Streets...................................................................625 Islands ............................................................................................................................... 625 General Characteristics................................................................................................ 625 Channelizing Islands.................................................................................................... 627 Divisional Islands........................................................................................................ 629 Refuge Islands ............................................................................................................ 630 Island Size and Designation.......................................................................................... 631 Island Delineation and Approach Treatment.................................................................. 632 Turning Roadways With Corner Islands ............................................................................... 638 Right-Angle Turns With Corner Islands.................................................................638 Oblique-Angle Turns With Corner Islands .................................................................... 641 Free-Flow Turning Roadways at Intersections ...................................................................... 643 Superelevation for Turning Roadways at Intersections .......................................................... 643 General Design Guidelines........................................................................................... 643 Superelevation Runoff ................................................................................................. 646 Development of Superelevation at Turning Roadway Terminals ..................................... 646 General Procedure ...............................................................................................647 Turn-Lane Cross-Slope Rollover...........................................................................652 Superelevation Transition and Gradeline Control....................................................652 Traffic Control Devices....................................................................................................... 653 Intersection Sight Distance.................................................................................................. 654 General Considerations ................................................................................................ 654 Sight Triangles............................................................................................................ 655 Approach Sight Triangles .....................................................................................655 Departure Sight Triangles.....................................................................................657 Identification of Sight Obstructions Within Sight Triangles.....................................657 Intersection Control..................................................................................................... 658 Case A—Intersections With No Control.................................................................658 Case B—Intersections With Stop Control on the Minor Road..................................660 Case B1—Left Turn From the Minor Road............................................................660 Case B2—Right Turn from the Minor Road...........................................................667 Case B3—Crossing Maneuver from the Minor Road..............................................667 Case C—Intersections With Yield Control on the Minor Road................................670 Case C1—Crossing Maneuver From the Minor Road.............................................670 Case C2—Left- and Right-Turn Maneuvers...........................................................675 Case D—Intersections With Traffic Signal Control.................................................675 Case E—Intersections With All-Way Stop Control.................................................678