Test: Geometric Design of Highways

All the geometric design features are worst affected by velocity of the vehicle only.

The most elevated or the highest portion of a pavement is called as a crown, whereas camber is the portion that is raised for drainage purposes.

Extra width of pavement is provided on horizontal curve to avoid the skidding, if the vehicle negotiates the curve then the centrifugal force will act towards outside and there is a chance of skidding, to avoid this extra width is provided.

A transition curve is introduced between horizontal curve and circular curve, the transition curve slowly introduces the centrifugal acceleration to avoid the danger of skidding.

The road user characteristics, traffic and vehicular characteristics mostly influence the road geometric design but the most important factor is speed of vehicle.

The ruling speed up to a cross slope of 10% is 100kmph; it decreases with increase in increase of cross slope.

The super elevation is a portion of pavement raised on outer edge with respect to inner edge or both edges raised with respect to centre.

 During rainy season the roads are usually flooded with water so to keep the pavement dry they have to be drained off so the road is provided with a camber.

The legal axle load used for design of pavements is 8.2 tonnes; usually they are expressed in MSA (million standard axles).

 In India generally there is always a mixed traffic flow except during midnight hours and early morning hours, so the designer has to assume mixed traffic flow only.