Stopping Distances

[Homer55]

Does anyone know the rule to woring out stopping distances, i used to know it but its 10 years ago since i took my test, any help would be appreciated.

[JOHNNYxCASH]

Hi Homer,

Hope this helps:-

(Calculation) (MPH) ( Overall Stopping Distance)

2 x 20 = 40 feet 12 metres 3 car lengths
2.5 x 30 = 75 feet 23 metres 6 car lengths
3 x 40 = 120 feet 36 metres 9 car lengths
3.5 x 50 = 175 feet 53 metres 13 car lengths
4 x 60 = 240 feet 73 metres 18 car lengths
4.5 x 70 = 315 feet 96 metres 24 car lengths

[kempie]

In 'the good old days' of imperial measure the stopping distances could be readily calculated using the formula

Thinking distance (ft) = Speed (mph)
Braking distance (ft) = Speed squared � 20

thus

40 mph = 40 ft + 80 ft (1600 / 20) = 120 ft
50 mph = 50 ft + 125 ft (2500 / 20) = 175 ft


To update this to the current imperial/metric mix requires

Thinking distance (m) = Speed (mph) x 0.3
Braking distance (m) = Speed squared � 66

Easy!

[Toureman]

Johnny's answers are all spot on, perhaps he and I are the only people in the country who still have a Highway code.

They are completely irrelevant to reality as they were last updated in the 1940s I think. !

[chevrolet1.8]

i think it's now - between 0500 and 0700 don't worrry about it, and after that it's nose to tail anyway.