What distance does it take to stop traveling at 50 mph?

Answer 1

The distance to stop depends upon a lot of factors, eg:

• type of road surface
• condition of tyres
• state of road surface (icy, dusty, wet, dry, etc)
• effectiveness of brakes

The stopping distance given in the Highway Code is based on assumptions that have not changed even though brakes, etc have improved. They are calculated as distance to stop in ft = (speed in mph)² ÷ 20

For 50 mph the physical stopping distance is 50² ÷ 20 = 125 ft

The Highway Code gives the emergency stopping distance as this distance plus the thinking distance which is given as 1 ft per mph which at 50 mph is 50 ft

These distances are converted to metres:

Emergency stopping distance = thinking distance + physical stopping distance

= 50 ft + 125 ft = 175 ft

≈ 15 m + 38 m ≈ 53 m

This is the shortest distance based on good brakes, good tyres, dry road. For worn tyres, wet or icy roads, etc increase the distance by a factor of 2, 5, 10 etc.

Answer 2

The answer depends on a large number of factors, including

• driver's response time,
• condition of the brakes,
• condition of the tyres,
• the road surface
• mass of the vehicle.