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4CardsMan
Aug 4, 2014, 04:53 PM
A passenger van is traveling at 60MPH in rain on a wet two-lane road. As he rounds a curve, the driver enters a long bridge. Too late, he notices that there are cars in both lanes approaching him at high speed.
With no sideways exit possible, he must stop the van and exit in the opposite direction. Assuming he possesses anti-lock brakes and the requisite skill, is it faster for him to (1) send the van into a spin allowing it to spin several times until stopped, or (2) put the van into a half-spin (turning it 180 degrees), and simply brake until stopped?
Anticipating objections, it is well known that at high speeds on dry pavement, a car handles very similarly to one traveling on ice at low speed and that a skillful driver can initiate and terminate a spin at will. I am guessing that 60 mph on wet road would simulate low speed on ice.

cdad
Aug 4, 2014, 06:18 PM
Is this homework? Im asking because there is a third answer that isnt in the equation. The two suggested answers to the problem would be very dangerous to attempt as passenger vans are top heavy. More then likely resulting in it turning over with either of the methods.

4CardsMan
Aug 5, 2014, 04:09 AM
Not homework. Danger is not an issue. If you know the answer, would you please share it?

smoothy
Aug 5, 2014, 04:54 AM
If danger is not an issue... then its not a realistic discussion and everything else really becomes moot... because only in homework could such important aspects be ignored.

cdad
Aug 5, 2014, 09:02 AM
The best way is to stop in a straight line taking advantage of the antilock brakes. Then shift to reverse. Accelerate to full speed and spin the van while shifting from reverse to forward while the momentum is with you thereby changing directions in the most minimal time.

ebaines
Aug 6, 2014, 05:02 AM
This is clearly NOT a homework question, but just idle curiosity.

Spinning the van does no good - as after turning around you would still be sliding towards the oncoming cars but going backwards. Since sliding tires offer virtually no grip, when you're sliding (as in spinning) the van won't be slowing down very much. Better to do as cdad suggests - however, there is a faster way to stop than using the brakes so hard that ABS kicks in. It's a technique called threshold braking, in which you press the brakes very hard but just shy of initiating ABS. If ABS activates it means the wheels have locked up and the car is sliding, so applying brake pressure just short of lock up provides better stopping than ABS. It takes some practice to get it right - we actually teach this skill at car club driving school events that I've attended. Once the car is stopped, throw it in reverse as cdad suggests.