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This may very basic, elementary and possibly dumb question but I have to ask.

Why, when parking uphill, driver should steer tires away from curb? Won't steering toward curb also can stop car by rear wheels? Think about it, the car will head in reverse towards the curb, in case if It's break fails, and curb should stop it from back from rolling further.

I guess steering away is more efficient because in other case due to weight of car and due to distance(because rear tires are straight) it may gain a little momentum and roll up on the obstacle of curb and may roll on further dangerously. Is this the theory behind this traffic advice and rule?

EDIT I guess the angle of tire with which it will make contact with curb also makes a difference. Front tires makes a better i.e bigger angle against curb and hence may be a better stopper.

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    $\begingroup$ Your instinct is right. The only problem is your understanding of the word "steer". $\endgroup$ – Mike Dunlavey Feb 23 '17 at 15:20
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    $\begingroup$ @mike can you be more clear on that? $\endgroup$ – old-monk Feb 23 '17 at 15:26
  • $\begingroup$ I've always somewhat questioned this reasoning as well (though it's mentioned enough I'm sure they have evidence to back it up). If your tires are able to go over the curb under the influence of gravity, steering away will actually make your car turn right into the road, while turning towards the curb will make your car go over the curb if the back wheels could get over. I assume on a reasonable incline the tire should never have enough energy from gravity to jump the curve, but that's entirely a guess at why this system holds. $\endgroup$ – JMac Feb 23 '17 at 15:47
  • $\begingroup$ @SaurabhTripathi: Your (correct) instinct is that you should turn the steering wheel so that if the car rolls downhill, the front wheels will roll into the curb and be stopped. So let's see, if you live in India and park on the left-hand side of the road, and you park up-hill, you want to turn the front wheels so that if the car rolls backward, it will roll into the curb - i.e. turn them to the right. If the word "steer" implicitly assumes moving forward then that could be called "steering away from the curb", but you are guarding against backward motion, not forward. $\endgroup$ – Mike Dunlavey Feb 23 '17 at 16:37
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The direction the wheels should be turned, when parked facing uphill, is chosen to minimize how far out into the traffic lane the car will protrude before it comes to rest against the curve.

If the front wheels are turned toward the curb, the rear wheels are what will come to a stop against the curb. For this to happen, the whole car has to roll backward far enough that the axis of the car makes an angle with the curb. To do this the front end has to stick out in the traffic lane.

If the front wheels are turned away from the curb, the car has to roll back only a short distance before the front wheels come to a stop against the curb. To do this the rear end doesn't have to move into the traffic lane much at all.

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  • $\begingroup$ I guess difference won't be more than the radius or diameter of tire, say 1 foot, which doesn't seem to be significant. $\endgroup$ – old-monk Feb 23 '17 at 17:49
  • $\begingroup$ Yes it is. If you roll too much the front wheels will tend to straighten out and you may skim or never hit the curb. You want the front wheels, which can rotate right or left, to stop as soon a s possible. $\endgroup$ – Bob Bee Feb 24 '17 at 2:07

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