Re: ABS

[Phil@sievers.demon.co.uk (Phil Payne)]

In message <199412091414.JAA08568@lombard.MOTOWN.GE.COM> John Greenstreet writes:
> 
> A human actuating a single brake pedal cannot possibly adjust the braking
> on four separate wheels forty times per second!  However, the best
> old systems managed only 10 per second, and even some new ones--like
> in Saturns--pulse only a few times per second.  A human can easily
> outperform the low-budget Saturn system.  No one would ever lump
> the performance of an 8086 with that of a Pentium, and the same
> should not be done with these systems over the same time period.

Well, my ur-quattro's six years old, and the pulsing is more like 15Hz!
 
I agree with what you say, in large measure.  But you overlook the fact that 
the human driver can synchronise steering movements with his "off brake" 
moments and avoid wheel movements during brake depressions.  Obviously, there 
has to be a reason why ABS was fitted to Formula 1 cars - and the reason was 
that it outperformed even the best drivers in the world.  For the amateur 
driver, ABS is dangerous in that it instills a level of confidence that may be 
unjustified - the coefficient of friction on ice is unchanged, as is the mass 
and velocity of the vehicle.  Miracles, regrettably, remain the prerogative of 
others.  Anyway, I (and a good many of my ex-colleagues) remain convinced that 
the ABS system fitted to the Ford Granada (the first car in the UK to have ABS 
as a standard feature) lengthened braking distances.  Interestingly, we managed 
to convince the company's insurers that giving ABS-trained drivers non-ABS cars 
whilst their own were being serviced was potentially dangerous.

Phil Payne
Sievers Consulting UK
Vice Chair, UK Computer Measurement Group
+44 385 302803 Fido 2:2503/415  CIS 100012,1660