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 -

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.

IMPORTANT INFORMATION

Although the information given below is that shown in the current UK Highway Code and as given on the official government site I have received the following comments which should be heeded.

Your advice on "thinking time" for drivers (shown below) is very much out of date. 

Those of us who have the misfortune of having to investigate and analyse road crashes have long realised through numerous studies that an approximate thinking time for driver's is about 1.5 seconds not the 0.67 seconds you are suggesting. 

The 1.5 seconds quote is an estimation only as many factors do come into play as pointed out be 'Joe'. 

Applying 1.5 seconds to your 20 mph (32 kmh) example will give a distance of 43.6 ft (13.3 m) not the 20 ft (6 m) quoted. Perception/reaction time is a very complicated subject and should not be treated lightly. Hope this helps in your understanding.

John Ruller

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

See comments above

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)

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