01 introduction&concepts-traffic ( Transportation and Traffic Engineering Dr. Sheriff El-Badawy )

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

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

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



AASHTO, 2001.

4

Design Vehicle

Passenger Car (P) Single Unit Truck (SU)

Intercity Bus (BUS-40) Intercity Bus (BUS-45)



AASHTO, 2001.

Design Vehicle

School Bus (S-BUS-36) Semi-Trailer (WB-40)

Semi-Trailer (WB-65)SOURCE: A Policy on Geometric


AASHTO, 2001.

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

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

Cut Section

Dead Sea Jordan

8

Typical Cross Section in Rural Road

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زراعة ال

(1.64)

(2.55)

(1.69) سوب ن م

زراعة المروه ال

ترحه ق م ال

1.5%2.0% 2.0%

5.5 m1.0 m 1.0 m

ق طري هر ال نتف ك

ق طري ال

تف ك

ق طري ال

1.5%

9.30 m

9



with Median

10

Typical Cross Section in Urban Road

without Median

Typical Cross Section in Urban Roadwithout Median

11

Typical Cross Section of Urban Road

with Median

Typical Cross Section in Urban Roadwith Median

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

LocalCollectorArterial

Functional Class minorMajor

3.03.33.63.6Min. Lane Width

(m)




(m)

Minimum Lane Width for Urban Roads




(m)




(m)

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

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

Minimum Median Width for Rural Roads



3.03.33.63.6Min. Width (m)

Minimum Median Width for Urban Roads



3.03.33.63.6Min. Width (m)

*Minimum width = 15 m for desert roads

Sharja, UAE

Moscow, Idaho UI Campus

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

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 ي ل نهائ سوب ال ن م ال

م قائ ساس ال قه اال ب ط

سم 10 سمك شطه ب ه مم سان خر

لت ف س قات اال ب ط

سم 15

سم 10

سم 15

سم 15

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

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

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.

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ه ي ت ي وم ار ادلل ساس من الاجح ه ا ق ب مس ط 25

مس ك 3 مس مس 30 * 30 يع راب الط ت ب

ك عد ادلم مس ب 15 سمك فه ي ظ قه رمل ن ب ط

ه ي سان ر ه خ ردور 100 ب 15 30 15 12,5ه ي ت ن ه امس سان ر مس خ 10

سم 4 سمك يه سطح لت ف س قه ا ب طسم 6 سمك طه لت راب ف س قه ا ب طير س ك ساس من احجار ت قه ا ب ط

دمك عد ال سم ب 25 سمك سارات ك? 1,5

Sidewalk Detail

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

Maximum Longitudinal Grades

Rural CollectorRural Local

Rural Arterial

Rural & Urban Freeways

Roadside Barriers & Guard rails

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

10

25

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

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.