The Virginia Department of Transportation (VDOT) revised its Road Design Manual in 2008 to include a policy statement on roundabouts. The policy says that “[...when a roundabout is feasible] it should be considered the Department’s preferred alternative due to the proven substantial safety and operational benefits. This is one of the stronger policy statements of any state in the United States. However, it has been difficult for VDOT to consistently implement and adhere to this policy on intersection projects throughout the state without a supporting process and/or tool and appropriate guidance. Timmons Group and Kittelson & Associates, Inc. were hired to develop a repeatable process and series of tools to quickly and efficiently evaluate roundabouts. The intent was to create a procedure that could be used early in project planning and continue through project design. Presented by Andy Boenau and Chris Tiesler at the Transportation Research Board's 4th International Conference on Roundabouts.

1. Statewide
Roundabout
Guidance
TRB 4th International Conference on Roundabouts
April 17, 2014
Andy Boenau
Chris Tiesler

2. Andy Boenau
1.Background
Part
Statewide
Roundabout
Guidance

3. Option A = familiar throughout the U.S.;
lots of death & destruction
Option B = familiar throughout the world;
lots of life & prosperity
Intersection Design Options

5. “We connect land use
(said every DOT everywhere)

6. Virginia DOT
Transportation & Land Use
Publications
“fundamental modes”
“enhance quality”

7. “…[roundabout] should be considered
the Department’s
preferred alternative…”
Virginia Policy

8. If feasible, then preferred.
Why?

9. If feasible, then preferred.
Why?

10. Since single-lane roundabouts are the
safest form of at-grade intersection,
why aren’t there more
in Virginia?

11. Institutional bias
and the fear of change.

13. Roundabout
1.Yield to traffic already in roundabout.

14. Traffic Signal
1. If the signal is a red ball, come to a complete stop
a) After stopping, you may turn right but must yield to oncoming traffic; except if the sign says "NO TURN ON RED", you cannot
b) After stopping, you may turn left on red from a one-way street onto a one-way street but must yield to oncoming traffic
2. If the signal is a green ball
a) you may go straight or turn right, but only if the way is clear - you must yield to vehicles still in the intersection
b) you may turn left but must yield to oncoming traffic
3. If the signal is a yellow ball
a) you may go straight or turn right
b) you may turn left but must yield to oncoming traffic
4. If there is one signal head for several lanes, it applies to all those lanes; if there is a signal head for each lane, each lane is governed by its own signal head; and if
there are multiple heads but not as many as there are lanes, generally a head centered above a lane governs that lane, a single head located above the line dividing
two lanes governs both lanes, and a single head centered above three lanes governs all three lanes
5. If the signal for your lane is a red arrow pointing left or right, come to a complete stop
a) After stopping, you may turn right on red but must yield to oncoming traffic; except if the sign says "NO TURN ON RED", you cannot
b) After stopping, you may turn left from a one-way street onto a one-way street ; except if the sign says "NO TURN ON RED", you cannot
6. If the signal for your lane is a red arrow pointing up, you may not go straight
7. If the signal for your lane is a green arrow pointing left or right, you may turn in the direction of the arrow, after yielding the right-of-way to vehicles within the
intersection, even if the red light is burning at the same time
8. If the signal for your lane is a green arrow pointing up, you may go straight, after yielding the right-of-way to vehicles within the intersection, even if the red light is
burning at the same time
9. If the signal for your lane is a yellow arrow, it means the same thing as the yellow ball, but applies only to movement in the direction of the arrow
10. If the signal is a blinking red ball, come to a complete stop and then enter the intersection, except you must yield to other vehicles already in the intersection
11. If the signal is a blinking yellow ball, enter the intersection with caution, except you must yield to other vehicles already in the intersection
12. If none of the bulbs on the signal head are illuminated (power outage), come to a complete stop and then enter the intersection with caution, except you must
yield to other vehicles already in the intersection
*special thanks to Ken Sides

15. A motorist has to make a lot of decisions
before driving through a traffic signal...
even when they aren’t fatigued or distracted.

16. If the general public trusts us
[deadly] status quo?
to design safe infrastructure, can we
make progress by following the

17. Transportation engineers now have
a much broader perspective about
the purpose and use of streets.
Complete street
Tactical urbanism
Walk to school
Arts district
Crosswalks
Bus shelters
Traffic calming
Livable street
Economic development
Bike to school
Less parking
Separated bike paths
Road diet
Placemaking

18. We have the engineering knowledge base.
We have a strong roundabout policy.
So how do we build
more roundabouts in Virginia?

19. 2.Process + Tools
Part
Chris Tiesler
Statewide
Roundabout
Guidance

20. Background
State agencies with successful roundabout programs generally
have
 Policy statement
 Process
 Internally apply the intent of the policy
 Tools
 Assist in performing assessments
VDOT has a strong policy, but has lacked a process and tools
to consistently implement and adhere to its policy

21. Three Tools
Screening Guidance
 Planning-level feasibility
Spreadsheet Tool
 Compare control forms
 Go beyond operations
 Easy to use/maintain
 User Manual companion
Design Guidance
 Principle-based
 Resource

22. Tool #1: Planning-Level Screening Document
Determine General Lane Needs
Figure 1 – Planning Level Daily Intersection Volumes (NCHRP Report 672 Exhibit 3-12)
0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
45,000
50,000
0% 10% 20% 30% 40%
Left-Turn Percentage
AADT
Double-lane roundabout
likely to operate acceptably
Single-lane roundabout may be
sufficient (additional analysis needed)
Single-lane roundabout
likely to operate acceptably
Double-lane roundabout may be
sufficient (additional analysis needed)
Planning Level Daily Intersection Volumes (NCHRP Report 672 Exhibit 3-12)

23. Planning-Level Screening
Right of Way
 Determine approximate footprint
Figure 1 – Planning Level Daily Intersection Volumes (NCHRP Report 672 Exhibit 3-12)
Adapted from NCHRP Report 672 (Exhibit 6-9)
Rounda bout C onfigura tion
Typic a l D es ign
Ve hicle
C om m on Ins c ribe d C ircle
D ia m e te r Ra nge *
Mini-Roundabout SU-30 45 to 90 ft
Single-Lane Roundabout B-40 90 to 150 ft
WB-50 105 to 150 ft
WB-67 130 to 180 ft
Multilane Roundabout (2 lanes) WB-50 150 to 220 ft
WB-67 165 to 220 ft
Multilane Roundabout (3 lanes) WB-50 200 to 250 ft
WB-67 220 to 300 ft
* Assumes 90-degree angles between entries and no more than four legs. List of possible design
vehicles not all-inclusive.

24. Planning-Level Screening
Approximate magnitude/size of roundabout and associated
impacts can be initially judged
Consider:
 Right of way
 Environmental
impacts
 Utilities
 Topography
Figure 1 – Planning Level Daily Intersection Volumes (NCHRP Report 672 Exhibit 3-12)

25. Planning-Level Screening
Network Interactions
 Consider site and surround intersection(s) in close proximity
Intersection spacing?
Adjacent traffic control – related queuing characteristics
Corridor considerations
Roundabouts particularly desirable when:
 Low percentage of through trips and high percentage of turns
 Safety improvements desirable
 Community enhancement/aesthetics
 Traffic calming
 High number of U-turns
 Unusual geometry creates design and signal phasing challenges
Figure 1 – Planning Level Daily Intersection Volumes (NCHRP Report 672 Exhibit 3-12)

26. Tool #2: Spreadsheet Tool
Compares life-cycle costs of roundabout to traffic signal or
stop-control across range of criteria
Elements included:
 Safety
 Vehicular delay
 Operations and Maintenance
 Capital design and construction costs
 Right-of-way cost
Elements not included:
 Emissions and fuel consumption
 Other qualitative elements

27. Key Takeaways
Easy to use
Requires basic information that is readily available
Evaluate criteria beyond traffic operations
 BETTER DECISIONS

28. What do I need?
Opening year and design year ADTs
Recent turning movement counts
Operational analysis to determine:
 Turn lane requirements
 Control delay
 Basic geometric layout
Historical crash data (optional)
Preliminary cost estimate
User is prompted for additional detail as needed (case-by-case)
 Assumptions can be made
 Straightforward inputs

29. Introduction Tab
Provides spreadsheet
navigation
instructions
Color Coding
 Orange cells indicate required
data entry
 Blue cells indicate optional
data entry
 Red text provides further
instruction

30. MainENTRY Tab
User-friendly drop list fields
allow for easy scenario
selection
Non-applicable fields
blocked out in gray

31. Highway Safety Manual Content
Part C – Predictive Method
 10: Two-Lane Rural Highways
 11: Multilane Rural Highways
 12: Urban and Suburban Arterials
Part D – Crash Modification Factors
 13: Roadway Segments
 14: Intersections
 15: Interchanges
 16: Special Facilities
 17: Networks
Glossary
Part A – Introduction and
Fundamentals
 1: Introduction
 2: Human Factors
 3: Fundamentals
Part B – Roadway Safety
Management
 4: Network Screening
 5: Diagnosis
 6: Select Countermeasures
 7: Economic Evaluation
 8: Prioritization
 9: Safety Effectiveness Evaluation

32. AdjustSPF Tab
Data entered uses
HSM Part C CMFs
to complete the
SPF calculations
Only fields for
selected facility
type are shown

33. DelayENTRY Tab

34. VDOT Spreadsheet Tool - Results
Calculates the monetary
safety and delay benefit of
the roundabout
Compares to ops/maintenance
and initial capital costs
expenditures
Life Cycle Benefit/Cost Ratio

35. Spreadsheet Tool Summary
Spreadsheet tool compares intersection control forms across
wide range of criteria
 Operations
 Safety
 Costs
 Construction
 Operations/Maintenance (Life Cycle)
Easy to use and maintain
Supplements initial roundabout screening tool
User Manual provides detailed information regarding
methodologies

36. Tool #3: Design Guidance Document
Condensed design guidance for practitioners
Emphasize key principles
 Planning
 Economic Evaluation
 Public Involvement
 Operations
 Safety
 Design
 Design Vehicle
 Splitter Islands
 Truck Apron
 Non-motorized Users
 Curbs/Drainage
 Traffic Control Devices
 Illumination
 Landscaping

37. Next Steps
Roll out tentatively planned for July 2014 to coincide with
update to VDOT Road Design Manual
All three tools likely to be housed and available on VDOT’s
external Roundabouts website
http://www.virginiadot.org/info/faq-roundabouts.asp
Education & training for VDOT staff and consultant
community

38. Andy @Boenau
@timmonsgroup
Chris @ctiesler
@kittelson
TRB 4th International Conference on Roundabouts April 17, 2014
Be social
with us
during
#Rndbt2014