The mechanical extra widening required for 10.5 m wide pavement on a horizontal curve of radius R metre is given by
where l is the length of wheel base of vehicle in metres.
where, n = no. of lanes
For 10.5 m wide pavement,
The reaction time for calculation of stopping distance may be assumed as
The maximum design gradient for vertical profile of a road is
Ruling gradient is the maximum gradient within, which the designer attempts to design the vertical profile of a road.
On sag (or valley) curves the available sight distance is determined based on
The maximum; width of a vehicle as recommended by IRC is
Transition curves are provided on the approach to horizontal curves in order to
Transition curve is provided in horizontal alignment
The ideal form of curve for the summit curve is
Circular summit curve is ideal as the sight distance available throughout the length of circular curve is constant.
The off-tracking of a vehicle having a wheel base of 6.0 m and negotiating a curved path of mean radius 25 m is
The important factor considered in the design of summit curves on highways is
When a fast moving vehicle travels along a summit curve, the centrifugal force will act upwards, against gravity and hence a part of the pressure on the tyres and spring of the vehicle suspensions in relieved. So there is no problem of discomfort to passengers on summit curves, particularly because the deviation angles on roads are quite small. The only problem is designing summit curves is to provide adequate sight distances. The stopping sight distance or the absolute minimum sight distance should invariably be provided at all sections of the road system and so aiso on summit curves.