# Lateral acceleration definition when banking

1. Aug 9, 2011

### ihardtail

I understand what and in what direction lateral acceleration is on a flat surface. When a vehicle is on a banked turn however, is lateral acceleration in a direction parallel to the surface of the road, or is it essentially in the direction (or is) centripital aceleration?

2. Aug 10, 2011

### Mech_Engineer

In both cases (flat surface vs. banked turn) the net acceleration on the vehicle is composed of two elements:
• Centripetal acceleration
• Gravity
The difference between the two is the angle between the centripetal acceleration vector and the road surface. In the case of the flat road, centirpetal acceleration is parallel to the road; but in the banked turn it is at an angle which provides the vehicle with more frictional force.

A common calculation done in the case of banked turns is given a fixed turn radius and bank angle, what speed is needed for the resultant acceleration vector (cent. acceleration + Gravity) to be perpendicular to the road surface.