I was trying to drive up an icy hill with a front-wheel-drive car (2006 Honda Civic Hybrid) when the front tires lost traction and the car started to slide backwards. The car then easily spun sideways as it slid backwards making it veer left/right and I nearly hit a telephone pole.

I repeated this a few times hoping to get up the hill. It seemed like I had much better control of the car during the backwards slide if I shifted the car into reverse (instead of drive) the moment I lost traction. In reverse, it didn't seem like the car would spin sideways. In these "Reverse vs Drive Experiments", I think I was sliding backwards at about the same speed (just "riding the brake" and not touching the accelerator pedal), but the reverse mode still seemed much more effective at keeping my car straight (while drive mode seemed to cause a spin-out with more random left/right motion).

My conclusion is that I am much safer changing to reverse mode if I start sliding backwards. Is this expected?

  • 2
    $\begingroup$ Don’t post the same question in multiple places : mechanics.stackexchange.com/q/63656/10976 $\endgroup$ – Solar Mike Feb 13 '19 at 16:47
  • $\begingroup$ One I hope you have winter tires, two you may need chains, three or further driver training... $\endgroup$ – Solar Mike Feb 13 '19 at 16:49
  • $\begingroup$ @SolarMike It got closed over there for being off-topic, so why not? $\endgroup$ – bobuhito Feb 13 '19 at 17:12

The control of a typical motor vehicle is based on the traction of the steering wheels in relation to the surface on which it operates.

As you describe, your slipping is happening when you are attempting to travel forward, but gravity is interfering with your plans. In a forward gear selection, the wheels will attempt to continue to operate in that direction, constantly breaking traction with the road. This results in the described veering, as the vehicle no longer has appropriate guidance.

When you shift to reverse, the tires will rotate and gain some traction while the vehicle travels downward. This provides for steering control, just as you've described.

Even though you are "riding the brake," you are modulating the braking force from full-on to zero, but at the lower braking levels, the wheels are allowed to rotate in the direction of travel, providing steering control. In the forward gears, your braking force may also be full-on to zero, but at the lower braking levels, the engine is continuing to remove the traction desired.

You may also note that you can shift to neutral to accomplish the same (improved steering) results.

  • $\begingroup$ Exactly. No matter the cause of a skid, the first thing to do is try to regain traction. Only then try to regain steering control. $\endgroup$ – Carl Witthoft Feb 13 '19 at 18:35
  • $\begingroup$ Ok, for the front wheels, let's just say static friction (when in reverse) is 50% higher than sliding friction (when in drive). It felt like there was something more going on, like the back tires were prevented from going backwards when in drive mode, but maybe not...I'll give you the answer if no one explains another effect. So, why can't I find references on the internet recommending putting my car into reverse if I'm ever sliding backwards? This dangerous situation must happen to thousands of people every year. $\endgroup$ – bobuhito Feb 13 '19 at 21:41
  • $\begingroup$ With a manual transmission, you don't need to go into reverse. Depressing the clutch and using the brakes carefully is all you need to stop safely. After that, you need a shovel and/or some sand and grit to get moving uphill again! $\endgroup$ – alephzero Feb 13 '19 at 22:32

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