Safety Margins.
Safe Braking Margins
The aim in this session is to establish your capability of stopping your vehicle
in a given distance, together with your evenness and quickness to respond. The braking
capacity of vehicles will vary considerably, depending on the weight of the vehicle
and the compound and pressure of the tyres. Your ability to stop the vehicle in
a given distance will be assessed at times when you probably least expect it. Times
when the traffic light changes to amber and you are close to the lights, the amber
light will give you approximately two seconds warning before the red light. The
Following chart should explain the levels of braking you should obtain. If when
braking you push slightly with your left leg to stabilise yourself in the driver's
seat, braking should be more sensitive and precise.
|
This chart shows the average stopping distance which an alert driver would obtain
when driving a car which is in good condition on a dry sealed road. |
|
K.P.H. = Kilometres Per Hour. M.P.S. = Metres
Per Second. Av.B.D. = Average Braking Distance Metres. R.D.
= Reaction Distance Metres. Av.S.D. = Average Stopping Distance
Metres. |
|
K.P.H. |
M.P.S. |
Av.B.D. |
R.D. |
Av S.D. |
|
40 |
11.1 |
19.4 |
11.1 |
20.5 |
|
50 |
13.9 |
14.8 |
13.9 |
28.7 |
|
60 |
16.7 |
21.4 |
16.7 |
38.1 |
|
70 |
19.4 |
38.8 |
19.4 |
48.2 |
|
80 |
22.2 |
37.8 |
22.2 |
60 |
|
90 |
25 |
47.9 |
25 |
72.9 |
|
100 |
27.8 |
59.2 |
27.8 |
87 |
The practice in automatic vehicles of left foot usage for braking is claimed to
reduce reaction time, however, the use of the left foot in this way ignores its
purpose of bracing the body securely during heavy braking. Current thinking favours
the use of the right foot only for brake and accelerator pedals, but left-foot braking
may be used to an advantage when the driver is trying to enter a busy road. More
than half-a-second may be saved by not having to move the right foot from the brake
to the accelerator.