How much greater is the amount of traction needed because each car is traveling 40 mph rather than 20 mph?

The amount of traction needed increases significantly when a car's speed doubles from 20 mph to 40 mph due to the relationship between speed and kinetic energy. Kinetic energy is proportional to the square of the speed, meaning that at 40 mph, a car has four times the kinetic energy compared to 20 mph. Consequently, this increased energy requires significantly more traction to maintain control and prevent skidding, especially during braking and cornering. Thus, the demand for traction is not just doubled but increased by a factor of four when the speed is doubled.