Colorado CDL Practice Test

How does doubling your speed affect the impact and braking distance?

1. 2x greater impact, 2x longer braking distance

2. 3x greater impact, 3x longer braking distance

3. 4x greater impact, 4x longer braking distance

4. No change in impact or braking distance

The correct answer is: 4x greater impact, 4x longer braking distance

Doubling your speed has a significant effect on both impact force and braking distance due to the principles of physics, specifically the laws of motion and the concept of kinetic energy. When you increase your speed, the kinetic energy of the vehicle increases with the square of the speed. Kinetic energy is computed using the formula KE = 1/2 mv², where 'm' represents mass and 'v' represents velocity. If you double your speed, the velocity (v) squared means that the kinetic energy increases four times. This increase in energy directly translates to a far greater impact force in an accident scenario, which is why the impact is considered to be four times greater. Additionally, braking distance is also affected by speed in a similar manner. The distance required to stop a vehicle is proportional to the square of the vehicle's speed. When you double the speed, the braking distance increases by a factor of four, meaning that it takes much longer to bring the vehicle to a stop. This interplay between speed, kinetic energy, and braking distance exemplifies why the effect of doubling speed results in both a fourfold increase in impact severity and a fourfold increase in braking distance, highlighting the crucial importance of speed management for safe driving.