Module 3: Geometric design of highways

Lecture 16 Horizontal alignment III

1

2

3

4

5

6

7

8

9

10

Curve Resistance

When the vehicle negotiates a horizontal curve, the direction of rotation of the front and the r ear wheels are different. The front wheels are turned to move the vehicle along the curve, whereas the rear wheels seldom turn. This is illustrated in figure 1.

Figure 1: Curve resistance

The rear wheels exert a tractive force $T$ in the PQ direction . The tractive force available on the front wheels is $T cos \alpha$ in the PS direction as shown in the figure 1. This is less than the actual tractive force, $T$ applied. Hence, the loss of tractive force for a vehicle to negotiate a horizontal curve is:

$$CR=T-T\cos\alpha$$ (1)