How To Curve Studies Curve studies look at two types of curvature, horizontal and vertical. Horizontal curves affect the handling of the car and their postings are based on driver comfort and the ability of vehicles to stay on the road.
Vertical curves affect how far a driver can see obstructions in the road or other vehicles.
If the vehicle's speed is too great the vehicle will slide off the side of the road. The safe speed on a curve does not account for the effects of snow, ice, sand, or other substances on the road which may affect the tire's ability to grip the road. Horizontal curves are tested using a device called a ball-bank indicator. It consists of a steel ball in a steel glass tube. The ball is free to roll except for the damping effect of the liquid in the tube.