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APPROXIMATE
STOPPING DISTANCES TIP With thanks to Mr. Alex Beet Instead of having to learn all the data
contained in the table shown below there is a formula you can remember in order to
calculate the overall stopping distance, which is as follows:- x² ÷ 20 + x = Overall stopping distance in
feet. x = speed For example: If you are travelling
at 30 mph 30² ÷ 20 + 30 = (30 x 30) ÷ 20 + 30 = 900 ÷ 20 + 30 = 75 ft. Simon Harding
has kindly sent in a easier way to remember these - Braking distances for cars. Why
have such a complicated equation to work out a very simple formulae?
i.e. 1 x 20 = 20ft 1.5 x 30 = 45ft 2 x 40 = 80ft 2.5 x 50 = 125ft and so on.... Overall stopping distances (that
is thinking + braking distance) 2 x 20 = 40ft 2.5 x 30 = 75ft 3 x 40 = 120ft 3.5 x 50 = 175ft and so on.... Somewhat easier to work out than square
roots! Remember -
Thinking distance is the same as the travelling speed in feet e.g. 30 mph = 30 ft. thinking
distance, 60 mph = 60ft thinking distance. Tip When trying to visualise a distance it is useful to remember that
the length of an average car is approximately 15ft, therefore, 75ft would be about 5 car
lengths away. Another way of judging distances has been sent in by Frederick Petersen - this uses a time factor. "Pick a fixture on the side of the road (such as a bridge or
telephone box) and allow a gap of 2 seconds between you and the rear of the car in front.
This is attained by saying in your mind 1001, take a breath then 1002. Should
the weather be wet then it is advised that an extra second would make a major accident
less likely." Along similar lines Neil
Gebbie suggests - "One thing I remember from a long
while back is for the 2 second gap, pick an object as the car in front
goes past and say, "only a fool, breaks the two second rule" it
takes 2 seconds to say and rings in your mind if you only say "only a
fool......." I must admit I have heard this before but
have found when trying to carry it out that cars keep popping in the gap in front and you
seem to be going backwards. Warning
sent in by Joe - Just a note to the stopping distances of a
vehicle....these facts and figures are for a driver who is alert and well
rested, in good health and not impaired by alcohol or medication. Weather and road conditions, as well
as type of vehicle and weight of load being carried can also affect these
stopping distance. SPEED THINKING
DISTANCE BRAKING DISTANCE OVERALL STOPPING DISTANCE 20 mph 20 ft. (6 m) 20 ft. (6 m) 40 ft. (12 m) 30 mph 30 ft. (9 m) 45 ft. (14 m) 75 ft. (23 m) 40 mph 40 ft. (12 m) 80 ft. (24 m) 120 ft. (36 m) 50 mph 50 ft. (15 m) 125ft. (38 m) 175 ft. (53 m) 60 mph 60 ft. (18 m) 180 ft. (55 m) 240 ft. (73 m) 70 mph 70 ft. (21 m) 245 ft. (75 m) 315 ft. (96 m) SPEED CONVERSION
MILES PER HOUR |
«» |
KILOMETRES PER HOUR (APPROX) |
MILES PER HOUR |
«» |
KILOMETRES PER HOUR (APPROX |
|
10 |
= | 16 |
80 |
= | 128 |
|
20 |
= | 32 |
90 |
= | 144 |
|
30 |
= | 48 |
100 |
= | 160 |
|
40 |
= | 64 |
110 |
= | 176 |
|
50 |
= | 80 |
120 |
= | 193 |
|
60 |
= | 96 |
130 |
= | 209 |
|
70 |
= | 112 |
140 |
= |
225 |