Design Speed of Highways - Geometric Design of Highways

The design speed of highways is defined as the maximum approximately uniform speed that is adopted by majority of the drivers. Design speed is one of the basic parameter which determines all the geometric design features. The design speed is dependent on the function of the road and the terrain conditions.

Designing the roads for very high speeds is not an economical option. Hence, roads has to be designed for a specific speed called as the design speed.

Table-1 below shows different design speeds for rural highways.

   

Important Features of Design Speed of Highways

• The ruling design speed is the guiding criterion for correlating various geometric design features.
• Where ruling design speed cannot be adopted, it is recommended to use minimum design speed.
• The design speed must stay uniform along the given highway.
• In highways, change in design speed is desirable, it is recommended to have a gradual change.

In certain countries like United Arab Emirates, a minimum speed must be maintained by all the drivers because a low speed can block the normal or reasonable movement of traffic. 

Design speed varies from 30 to 130km/hr with an increment of 10km/hr.

Also Read: