6 cross section elements ( Transportation and Traffic Engineering Dr. Sheriff El-Badawy )

المنصورة-قسم الهندسة المدنية –معهد مصر العالي للهندسة والتكنولوجيا

Introduction


Highway Cross Section Elements

• Travel Lanes (Carriageways)

• Shoulders

• Medians

• Roadside Barriers

• Curbs

• Gutters

• Guard Rails

• Sidewalks

• Side (cross) slopes

Principal Elements Marginal Elements


Typical Cross Section of Rural

Road

Highway Engineering, Tonias, D.


Typical Cross Section of Rural

Road


Typical Cross Section of Urban

Road


Typical Cross Section of Urban

Road


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 (2.75 m) may

be used.


Shoulder

• Shoulders usually range in width from 2 ft (0.6 m) for minor

local roads. (6 to 8 ft – 1.8 to 2.44 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 .


Medians

• A median is a wide strip of a highway used to separate

traffic traveling in opposite directions.

• Offer a recovery area for errant vehicles

• Provide an area for emergency stopping

• Serve as a safe waiting area for left-turning and U-turning

vehicles

• Decrease the amount of headlight glare

• Allow for expansion to future lanes

• Medians can be Flushed – Depressed- Raised.


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Moscow, Idaho UI Campus


Medians


Cross (Side) Slope

• The slope selected generally depends on the type of

pavement used.

• Typical cross slope of 1.5 to 3% is recommended.

• Cross slopes greater than 2% should be avoided (for

safety).


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

• Reduction of maintenance operation

Types of curbs:

Vertical curbs -- discourage vehicles from leaving the roadway,

not desirable on high-speed highways, desirable on urban

roads, and along long walls, tunnels to protect safety walks.

Sloping curbs -- vehicle can cross them readily when required,

used at median edges, to outline channelizing islands, at the

outer edge of the shoulder.

Curbs


Curbs

• Barrier Curbs• The purpose of a barrier curb is to prevent or limit the possibility of

a vehicle’s leaving the roadway.

• A general rule of thumb is that barrier curbs should not be used

when the design speed is greater than 40 mph.

• Mountable Curbs • A mountable curb offers the advantage that a vehicle can cross it

when necessary.




Sidewalks

• Sidewalks are an integral part of city roads, sometimes

provided in rural areas.

• In residential areas the sidewalk width varies between

1.2 to 2.4 m.



Roadside Barriers & Guard rails


Right of Way