Vehicle stopping distance

Hello,

I'm using torcs as part of a research project, to simulate an environment
where cars follow each other in a platoon.
In order to do this, we have to make some assumptions about how cars are
able to behave, namely what is the stopping distance in case of a full
brake.

According to some sites (e.g. http://www.csgnetwork.com/stopdistcalc.html),
the distance can be computed by the formula:

d = (v*v) / 2ug, where u is the coefficient of friction between the tires
and the road.

As far as I know, the coefficient is something like 0.75 for a typical road
and tires. According to this site:

http://www.roymech.co.uk/Useful_Tables/Tribology/co_of_frict.htm

It should be between 0,5-0,8. According to the first site, "For many newer
high performance tires with good tread, the coefficient of kinetic friction
on a dry road surface may approach 0.8 if the braking is not so prolonged as
to cause tire melting."

If you input a 0.8 coefficient in the formula, for a 22 m/s speed you get a
stopping distance of ~30.87 m (you can test it on the first site).

d = (v*v) / 2ug = (22*22) / 2 * 0.8 * 9.8 ~= 30.87 m.

In our simulation using torcs, the cars are braking much faster, with a
stopping distance of about 9.67 m for the same speed. Here are the complete
values:

m/s  distance
02   0.055786
03   0.163696
04   0.296387
05   0.486694
06   0.715820
07   0.991577
08   1.297729
09   1.672729
10   2.091309
11   2.507965
12   2.891869
13   3.508484
14   3.956104
15   4.603813
16   5.303360
17   5.959892
18   6.602043
19   7.316177
20   8.078354
21   8.800949
22   9.675278
23   10.018005
24   10.463196
25   11.150696
26   12.195404

This gives us a coefficient of friction of about 2.75, which (as far as I
can know) is not realistic.

So, my question are the following:

- Is torcs supposed to be realistic about stopping distances?
- Are the above stopping distances to be expected for a car of category
'Track-RWD-GrA'?
- Is it possible to change any parameter so that we obtain stopping
distances similar to realistic non-racing cars?

Thanks a lot for your support!

Best regards,
Luís Marques

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