If you double your speed, your vehicle will travel ________ as far to brake to a stop.

Explanation

Even after you start to brake, your vehicle will keep moving for a certain distance before it comes to a stop. This is called the braking distance. It is roughly proportional to the square of your speed. For example, doubling your speed from 30 mph to 60 mph will increase your braking distance by about a factor of four, from 46 feet to 180 feet. At higher speeds, leave a greater following distance behind the vehicle in front of you.