Traffic engineering aims to achieve efficient operation, safety, economic design and minimize environmental impact. Highway design considers factors like traffic volume, design speed, vehicle type, terrain, and level of service. Design hourly volume is used for calculations and is typically the 30th highest hourly volume. The design vehicle is the largest vehicle expected to frequently use the road and determines design standards. A highway cross section includes travel lanes, shoulders, medians, barriers, curbs, gutters, sidewalks and slopes. Right of way width must accommodate all highway elements and potential future expansion.

1. 1
Objectives of Traffic Engineering
• To achieve the following:
• Efficient Operation,
• Safety,
• Economic Design,
• Minimize the environmental impact.
Factors Influencing Highway Design
• Functional classification
• Design hourly traffic volume and vehicle mix
• Design speed
• Design vehicle
• Cross section of the highway, such as lanes, shoulders, and
medians
• Presence of heavy vehicles on steep grades
• Topography of the area that the highway traverses
• Level of service
• Available funds
• Safety
• Social and environmental factors

2. 2
Design Traffic Volumes
• Average Daily Traffic (ADT):
• Daily basis
• Both directions
• Annual Average Daily Traffic (AADT):
• Annual traffic averaged on daily basis
• Both directions
• Design Hourly Volume (DHV):
• Traffic volume used for design calculations
• Typically between the 10th and 50th highest
volume hour of the year (30th highest is most
common)
Minimum Design Speeds for Local Rural Roads
Minimum Design Speeds for Rural Collectors
SOURCE: A Policy on Geometric
Design of Highways and Streets,
AASHTO, 2001.

3. 3
Design Vehicle
• A design vehicle is selected to represent all vehicles on
the highway.
• Its weight, dimensions, and operating characteristics are
used to establish the design standards of the highway
such as the turning radii at intersections, max. grades,
etc.
• The vehicle type selected as the design vehicle is the
largest that is likely to use the highway with
considerable frequency.
Design Vehicle Dimensions
SOURCE: A Policy on Geometric
Design of Highways and Streets,
AASHTO, 2001.

4. 4
Design Vehicle
Passenger Car (P) Single Unit Truck (SU)
Intercity Bus (BUS-40) Intercity Bus (BUS-45)
SOURCE: A Policy on Geometric
Design of Highways and Streets,
AASHTO, 2001.
Design Vehicle
School Bus (S-BUS-36) Semi-Trailer (WB-40)
Semi-Trailer (WB-65) SOURCE: A Policy on Geometric
Design of Highways and Streets,
AASHTO, 2001.

5. 5
Design Vehicle
• Passenger car (P)  the main traffic generator in a parking lot
or series of parking lots.
• Single-Unit Truck (SU)  intersection design of residential
streets and park roads.
• City transit bus  state highway intersections with city streets
that are designated bus routes and relatively few large trucks.
• Large School Bus (84 passengers) or Conventional School
Bus (65 passengers) may be used for the design of
intersections of highways with low-volume county highways and
township/local roads under 400 ADT.
• WB-65 or 67 is the minimum size of the design vehicle at
intersections of freeway ramp terminals and arterial crossroads,
and at intersections of state highways and industrialized streets
that carry high volumes of traffic.
Cross Section Elements
.

6. 6
Highway Cross Section Elements
• Travel Lanes (Carriageways)
• Shoulders
• Medians
• Roadside Barriers and
Guard Rails
• Curbs and Gutters
• Sidewalks
• Cross slopes
• Side slopes
Principal Elements Marginal Elements
Typical Cross Section of Rural Road
Highway Engineering, Tonias, D.

7. 7
Cut Section
Dead Sea Jordan

8. 8
Typical Cross Section in Rural Road
(1.69) ‫سوب‬ ‫ن‬ ‫م‬
‫زراعة‬ ‫ال‬
(1.64)
(2.55)
(1.69)
‫مروه‬ ‫ال‬
‫ترحه‬ ‫ق‬ ‫م‬ ‫ال‬
1.5%2.0% 2.0%
5.5 m1.0 m 1.0 m
‫ق‬ ‫طري‬ ‫ال‬ ‫هر‬ ‫ن‬
‫تف‬ ‫ك‬
‫ق‬ ‫طري‬ ‫ال‬
‫تف‬ ‫ك‬
‫ق‬ ‫طري‬ ‫ال‬
1.5%
9.30 m

9. 9
Typical Cross Section in Rural Road
Typical Cross Section in Rural Road
with Median

10. 10
Typical Cross Section in Urban Road
without Median
Typical Cross Section in Urban Road
without Median

11. 11
Typical Cross Section of Urban Road
with Median
Typical Cross Section in Urban Road
with Median

12. 12
Travel Lanes
• In general, the number of travel lanes should be based on
the design traffic volume and level of service.
• No. of travels lanes in both directions are usually equal.
• Travel lanes generally range in width from 10 to 13 ft.
(3 to 3.95 m).
• Typically is 12 ft (3.65 m)
• Under extreme circumstances, a width of 9 ft (2.70 m) may
be used.
• Lane width affects the LOS.
Minimum Lane Width for Rural Roads
LocalCollector
Arterial
Functional Class
minorMajor
3.03.33.63.6
Min. Lane Width
(m)
LocalCollector
Arterial
Functional Class
minorMajor
3.03.33.63.6
Min. Lane Width
(m)
Minimum Lane Width for Urban Roads
LocalCollector
Arterial
Functional Class
minorMajor
3.03.33.63.6
Min. Lane Width
(m)
LocalCollector
Arterial
Functional Class
minorMajor
2.703.33.63.6
Min. Lane Width
(m)

13. 13
Shoulder
• Shoulders usually range in width from 2 ft (0.6 m) for minor
local roads. (6 to 8 ft – 1.8 to 2.45 m- is preferred) to 12 ft
(3.65 m) for major highways.
• Typical cross slope is 3% for paved shoulders and 5% for
unpaved shoulders .
Graded and Usable Shoulder
Rounding = 1.2 to 1.8 m

14. 14
Shoulders (Cont’d)
• Shoulders may be surfaced either full or partial width.
• Materials used to surface shoulders include:
• Gravel,
• Crushed rock,
• Chemical additives,
• Bituminous surface treatments,
• Various forms of asphaltic or concrete pavements.
• Bituminous and concrete-surfaced shoulders should
be sloped from 2 to 6%,
• Gravel or crushed-rock shoulders from 4 to 6 %,
Medians
A median is a wide strip of a highway used to:
• Separate traffic traveling in opposite directions.
• Offer a recovery area for out-of-control vehicles.
• Provide an area for emergency stopping.
• Provide storage area for left-turning and U-turning
vehicles.
• Decrease the amount of headlight glare.
• Providing temporary lanes during maintenance operations.
• Allow for expansion to future lanes.
• Medians can be Flushed – Depressed- Raised.

15. 15
Minimum Median Width for Rural Roads
LocalCollector
Arterial
Functional Class
minorMajor
3.03.33.63.6Min. Width (m)
Minimum Median Width for Urban Roads
LocalCollector
Arterial
Functional Class
minorMajor
3.03.33.63.6Min. Width (m)
*Minimum width = 15 m for desert roads
Sharja, UAE
Moscow, Idaho UI Campus

16. 16
Medians
Cross Slope
• The slope selected generally depends on the type of
pavement used.
• Typical cross slope of 1.5 to 3%  High surface type
• Cross slopes greater than 2% should be avoided (for
safety).
• Typical cross slope of 2 to 6%  Low surface type

17. 17
Basic Cross Slope Arrangements for Divided Highways
(a) Each Pavement Slopes Two Ways
(b) Each Pavement Slopes One Way
A curb is a raised element that is used, among other things,
to denote the edge of a roadway.
Functions of curbs
• Drainage control
• Roadway edge delineation
• Enhanced appearance
• Right-of-way reduction
• Delineation of pedestrian walkways
Curbs
‫سم‬ 25
‫سم‬ 12
‫سم‬ 20
‫لت‬ ‫ف‬ ‫س‬ ‫ال‬ ‫ل‬ ‫ي‬ ‫نهائ‬ ‫ال‬ ‫سوب‬ ‫ن‬ ‫م‬ ‫ال‬
‫م‬ ‫قائ‬ ‫ال‬ ‫ساس‬ ‫اال‬ ‫قه‬ ‫ب‬ ‫ط‬
‫سم‬ 10 ‫سمك‬ ‫ب‬ ‫شطه‬ ‫مم‬ ‫ه‬ ‫سان‬ ‫خر‬
‫سم‬ 15
‫سم‬ 10
‫سم‬ 15
‫سم‬ 15

18. 18
Curbs
• Barrier Curbs
• The purpose of a barrier curb is to prevent or limit the possibility of
a vehicle’s leaving the roadway.
• Barrier curbs should not be used when the design speed is greater
than 40 mph (60km/hr).
• Mountable Curbs
• A mountable curb offers the advantage that a vehicle can cross it
when necessary.

19. 19
Gutters
• Gutters or drainage ditches are usually located on the
pavement side of a curb to provide the principal
drainage facility for the highway.
• They are sloped to prevent any hazard to traffic.
• Cross slopes of 5 to 8%.
• Width 0.3 m to 1.8 m wide.
• Gutters can be designed as V-type sections or as
broad, flat, rounded sections.

20. 20
Sidewalks
• Sidewalks are an integral part of city roads,
sometimes provided in rural areas.
• Min. 0.6 m for maintenance of bridges.
• In residential areas the sidewalk width varies between
1.2 to 2.4 m.
ÊÝÕ í áåÑÕ í Ý ÇáãÔÇå
‫ه‬ ‫ي‬‫و‬‫س‬ ‫ت‬ ‫ل‬ ‫ل‬ ‫مس‬ 3 ‫سمك‬ ‫يه‬ ‫ت‬ ‫ن‬ ‫سم‬ ‫ا‬ ‫ه‬ ‫مون‬ ‫قه‬ ‫ب‬ ‫ط‬
‫يه‬ ‫ت‬ ‫ي‬ ‫م‬‫و‬ ‫ادلل‬ ‫ار‬ ‫الاجح‬ ‫من‬ ‫ساس‬ ‫ا‬ ‫قه‬ ‫ب‬ ‫ط‬ ‫مس‬ 25
‫مس‬ 3 ‫ك‬ ‫مس‬ ‫مس‬ 30 * 30 ‫ع‬‫ي‬ ‫راب‬ ‫ت‬ ‫الط‬ ‫ب‬
‫ك‬‫ادلم‬ ‫عد‬ ‫ب‬ ‫مس‬ 15 ‫سمك‬ ‫فه‬ ‫ي‬ ‫ظ‬ ‫ن‬ ‫رمل‬ ‫قه‬ ‫ب‬ ‫ط‬
‫يه‬ ‫ن‬‫ا‬‫س‬‫ر‬‫خ‬ ‫ه‬ ‫ردور‬ ‫ب‬ 100 15 30 15 12,5
‫يه‬ ‫ت‬ ‫ن‬ ‫امس‬ ‫ه‬ ‫ن‬‫ا‬‫س‬‫ر‬‫خ‬ ‫مس‬ 10
‫سم‬ 4 ‫سمك‬ ‫يه‬ ‫سطح‬ ‫لت‬ ‫ف‬ ‫س‬ ‫ا‬ ‫قه‬ ‫ب‬ ‫ط‬
‫سم‬ 6 ‫سمك‬ ‫طه‬ ‫راب‬ ‫لت‬ ‫ف‬ ‫س‬ ‫ا‬ ‫قه‬ ‫ب‬ ‫ط‬
‫ير‬ ‫س‬ ‫ك‬ ‫ت‬ ‫احجار‬ ‫من‬ ‫ساس‬ ‫ا‬ ‫قه‬ ‫ب‬ ‫ط‬
‫دمك‬ ‫ال‬ ‫عد‬ ‫ب‬ ‫سم‬ 25 ‫سمك‬ ‫سارات‬ ‫ك‬
?1,5
Sidewalk Detail

21. 21
Min. Width of Sidewalks
• 1.5 m in residential areas.
• 2.5 m in industrial and commercial areas.
• 3.0 m in pedestrian bridges.
• 3.0 m in pedestrian crossings
Source: Egyptian Code (2008)
Minimum Grade
• Minimum grades depend on the drainage conditions of
the highway.
• Zero percent grades may be used on uncurbed
pavements with adequate cross slopes.
• For curbed pavements, a minimum of 0.5 percent which
may be reduced to 0.3 percent on high-type pavement
constructed on suitably crowned, firm ground can be
used.

22. 22
Maximum Longitudinal Grades
Rural Collector
Rural Local
Rural Arterial
Rural & Urban Freeways
Roadside Barriers & Guard rails

23. 23
20cm
8cm
20cm
8cm
1.0m
15
175165
60
17
85
20
Base Conc. Class 210/50
Const. Joint (Level)
Equally Spaced Preset in Base Concrete
3 NO. Each Side Per 2.5m Length of Unit
Staggered Dowel Bars ? 32 0.60m Long
Barrier Conc.
2cm Chamfer
1025
15 15
R=3
50
R=25
Reflector
Reflector
Colour: Red
Every 6.0m
Spacing:
Pre-Cast New Jersey Barrier Double Face
7
Paved shoulder
30
100
(Cast in situ)
30

24. 24
Right of Way
• Total land area acquired for the construction of a highway.
• The width should be sufficient to accommodate:
• All the elements of the highway cross section,
• Any planned widening of the highway,
• Public-utility facilities that will be installed along the highway.
The desirable minimum right of way
Two-lane urban collectors  12 m and 18 m.
Two-lane urban arterials  25 m.
Undivided four-lane arterials  19 m to 32 m.
Divided arterials  36 to 90 m.