What is ruling gradient in transportation engineering.

The ruling gradient or the maximum gradient with which the designer attempts to design the vertical profile of the road. This depends on the terrain, length of the grade, speed pulling power the vehicle and the presence of the horizontal curve. In flatter terrain, it may be possible to provide flat gradient, but in hilly terrain it is not economical and sometimes not possible also. The ruling gradient is adopted by the designer by considering a particular as the design and for a design vehicle with standard dimensions. But our country has a heterogeneous traffic and hence it is not possible to lay down precise standards for the country as a whole. Hence IRC has recommended some values for ruling gradient for different types of terrain.