average braking distance chart required

  Seth Haniel 14:07 16 Jan 2009

A friend asked me to find out car/motorbike stopping distances for her. Have speent last half hour with no luck been to Brake.org - tried Highway code- all to no avail.

any forum member know of chart/scale ?

  I am Spartacus 14:13 16 Jan 2009

click here bottom of page. There's also a PDF

  Seth Haniel 14:22 16 Jan 2009

I am Spartacus

some things are just too hard to find - when theyre under your nose.

  Stuartli 15:14 16 Jan 2009

Remember such figures are not cast in stone - it will be different for every driver and every vehicle and also depend on road surface and weather conditions.

Also see:

click here

click here

click here

Many more.

  Quickbeam 15:57 16 Jan 2009

"Remember such figures are not cast in stone"
Particularly in respect to the lorry stopping distances in the 3rd link.

A 6 axle artic will vary in weight from 14 tonnes unladen to 44 tonnes fully laden. This is a difference of 30 tonnes.

Beware when you cut in front of an obviously laden truck... we've all collected the trophies to prove the result:(

  skeletal 16:54 16 Jan 2009

There is some interesting advice on the posted links. You can also use the equations of motion in a spreadsheet and work it out for yourself as this give some interesting results:

Stopping distance = u x t + (u^2) / 2 x f

u = speed from which you are stopping
t = thinking time and time to move your foot to the brake pedal
f = deceleration


30 MPH; 1 second thinking/moving time; 0.9 x g deceleration (g is the acceleration due to gravity (32 ft/s/s) and a modern car should achieve around 0.9 g on a good road; note I said car, other vehicles are different).

Change units to ft/s
30 MPH x 22/15 = 44ft/s (the factor 22/15 changes MPH to ft/s)
f = 0.9 x 32 = 28.8 ft/s/s

u x t = 44 x 1 = 44 ft
u^2 / 2 x f = 1936 / 57.6 = 33.6

So total stopping distance = 77.6 ft

Which is not too far away from the various quoted distances.

However, in a spreadsheet you can now try changing the numbers and be amazed!

Those who have remembered my going on about left foot braking in automatic cars change the 1 second thinking/moving time to 0.5 seconds (easy to achieve, it could be as low as 0.2 seconds but we won’t go too far). You will now see that a “left foot braker” can stop, from 37 MPH, in the same distance as a “normal” driver can from 30 MPH.

Now put in 70 MPH, 1 second thinking, 0.9 g and get 285 ft (a bit lower than published), but change to 0.1 g and see 1750 ft. Do you want to try to stop from 70 on ice?

If you are tired/ill/drunk or decide it is good fun to text on your mobile while driving, change the 1 second thinking time to 3 seconds.

And so on.

And then decide whether or not it is sensible to sit 6 inches behind the driver in front, even at low speeds...


This thread is now locked and can not be replied to.

Elsewhere on IDG sites

Dell XPS 13 9370 (2018) review

HomePod review

Comment regarder les Oscars 2018 ?