For the people that practice street-math, Kinetic Energy goes as (velocity)^2. So halving the speed reduces the energy to 1/4. A third of the speed is 1/9th the

For the people that practice street-math, Kinetic Energy goes as (velocity)^2. So halving the speed reduces the energy to 1/4. A third of the speed is 1/9th the energy. etc. As you go faster, your energy goes up exponentially. This is why there are bitter fights about increasing the speed limit on roads; they become exponentially less safe (big caveats apply, naturally).