# Components of Highway Design and Construction

In highway, common elements are the road width, cross slope, pavement, road margins, traffic separators, and curbs. Design of these geometric elements is based on the psychology of the driver, the characteristics of the vehicle and the traffic of the area. In order to maintain the safety of highway, these elements should be controlled efficiently.

1. Cross Slope or Camber: Cross Slope or camber stands for the slope that is arranged transversally towards the pavement or carriageway. The cross slope can discharge the rainwater from the road surface. Insufficient cross slope leads to the flooding of water over the pavement and as a result the highway gets damaged.

The value of the slope is influenced by the type of materials utilized for road construction and the amount of rainfall in the area. Normally, the value of cross slope differs from 1 in 60 to 1 in 25.

2. Carriageway or Pavement: The pavement or the carriageway means the paved segment of the highway or the road over which the traffic is supposed to pass on. The width of the pavement is based on the width of the traffic lanes and the number of lanes planned for construction.

Traffic lane stands for the carriageway or the pavement that is designed for the movement of one line of traffic. Normally, for single lanes with a maximum width of 2.44m, the width of the lane should be 3.75m. For the pavements designed with two or more than two lanes, the width should be 3.5m.

3. Medians: Medians belong to traffic separators for resisting the collision of the vehicles which are moving in the opposite direction on the adjoining lanes.

4. Curbs: It is the boundary among the pavement and the shoulder. Curbs are specifically useful for urban roads.

5. Road Margins: Road margin comprises of the followings -

a. Shoulders
b. Bus Bays
c. Parking lanes
d. Sidewalks or footpaths

6. Width of Roadway: The width of roadway or the width of formation has similarity with the sum of the width of pavement (along with the separators if any) and the shoulders.

7. Right of Way: The area of the land provided for the road along its alignment is known as the right of way. Land width is called as the width of this acquired land. The right of way is influenced by the importance of the road and the scope of future development.