When you increase speed by a factor of 4, you increase the HARM by a factor of 16
The physical danger of a vehicle is governed by its kinetic energy equation: Ek = ½mv². Because velocity (v) is squared, any increase in speed increases kinetic energy disproportionately. For a standard modern passenger vehicle or SUV with a mass (m) of 2,000 kg (2 metric tonnes): • At Walking Speed (5 km/h): 5 km/h translates to approximately 1.39 m/s. The kinetic energy generated is 1,932 Joules. • At Low Driving Speed (20 km/h): 20 km/h translates to approximately 5.56 m/s. The kinetic energy generated spikes to 30,914 Joules. The Disproportionate Risk Factor: While the speed increases by a factor of 4, the impact energy increases by a factor of 16. A vehicle hitting a pedestrian at 20 km/h transfers 16 times more destructive force into human tissue than it does at 5 km/h. At 5 km/h, collisions typically result in bruising or minor bone fractures. At 20 km/h, the impact force routinely causes internal organ ruptures, severe compound fractures, and fatal head trauma from being thrown onto concrete surfaces.