Skidding downhill on black ice: survival tactics

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7782 posts

Uber Geek

#1826437 21-Jul-2017 11:37

gzt:
MikeAqua:

But ... that's rally-driver stuff, most people wouldn't pull it off in an unanticipated situation (I sure couldn't) and it probably wouldn't work unless you had a very aggressive tread pattern.

and then possibly the same end result at a higher speed and impact.

If you have lost traction you can't really increase your speed but if you claw in the opposite direction to an undesirable direction of travel you can lessen you speed and maybe recover.

I've never needed to try this with out warning on ice while driving (I'm very cautious in icy conditions) but I have done it under controlled conditions in FWD when I knew the ice was there.

Mike

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#1826487 21-Jul-2017 12:57

Azzura:

Like tdgeek says...
if your wheels are rolling then there is some kinda grip there. Before ABS, pumping the breaks is what you did (its hard to come over the natural instinct --- push the break harder when nothing is happening) --because a locked tire continues on in the direction the momentum was taking you...no mater where the locked skidding tire is pointing. I wouldn't be trying to gear down on black ice....you'd just break any grip you had.

Not sure barrel rolling the car is what I would be trying to do. How did you get rolling the car over?

I think, if we were living down on the south island in possible snow country and knowing (wife and I) what we know about snow/icy roads. We'd have some form of snow/ice capable tires on (for the season), that are good below 7C and above (our lives are worth it). And that is on all 4 wheels the same tires. Not just the front only...

Back home ---We use to go out in the car or a buds 4wd during snowstorms 30 to 40cms just for the fun of it (kinda miss it). Lets see if we can make it up this unploughed hill with snow drifts. doing donuts in parking lots.... During freezing rain storms (if you could get in your car), we'd still go out in the car (not doing donuts). If you had good tires you'd be alright drive accordingly (unless it was realllllyyyyy bad out!).

There's nothing wrong with normal tyres below 7C.

Unfortunately, they are hard, do not have the sipes to grip ice and snow, and most do not have enough grooves to clear snow.

Not sure what happens when you drive on snow tyres at 120kph when it's warm ... our Canadian friend might be able to tell us!

Sidestep

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#1826494 21-Jul-2017 13:10

Batman:

There's nothing wrong with normal tyres below 7C.

Unfortunately, they are hard, do not have the sipes to grip ice and snow, and most do not have enough grooves to clear snow.

Not sure what happens when you drive on snow tyres at 120kph when it's warm ... our Canadian friend might be able to tell us!

I used to swap on winter tires (& rims) each October, swap back to summer tires in April.

Summers in Alberta are often hot (30° and above). Having snow tires on then is like driving on marshmallows.

Azzura

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#1826529 21-Jul-2017 14:25

I wouldn't drive winter tires during summer....some fools do (Nov, winters went on...late, April summers went on). They will burn off and they don't perform as well as summer tires do in summer conditions. Summer tires for summer....winter tires for winter. All Seasons = jack of all trades, master of none!

Hmm 7 C you say....not sure what a normal tire is

https://www.thestar.com/autos/2014/11/19/at_7c_its_time_to_put_on_those_winter_tires.html

Azzura

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#1826530 21-Jul-2017 14:28

Sorry, if this becomes double post...but after idk how many years I can't seem to find the preview post.

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#1826853 21-Jul-2017 23:07

Azzura:

I wouldn't drive winter tires during summer....some fools do (Nov, winters went on...late, April summers went on). They will burn off and they don't perform as well as summer tires do in summer conditions. Summer tires for summer....winter tires for winter. All Seasons = jack of all trades, master of none!

Hmm 7 C you say....not sure what a normal tire is

https://www.thestar.com/autos/2014/11/19/at_7c_its_time_to_put_on_those_winter_tires.html

The original all seasons have been tested to be inferior to summer tyres in summer both wet and dry; and no better than summer tyres in ice and snow.

However, technology improves and the current gen of All seasons actually work in ice and snow, unlike the old gen ones ... but we can't get them. They try to distinguish them from the old all seasons by calling them "all weather" tyres ...

gzt

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#1826857 21-Jul-2017 23:41

I had a look at the detection side of it. It looks some distance to a consumer OEM product yet. There is a company providing detection with infra-red spectroscopy which cannot be cheap:

http://www.sensice.com.

A Princeton physics dissertation (pdf) covering IR and radar black ice detection:

https://www.princeton.edu/physics/graduate-program/theses/theses-from-2009/W.Chenthesis.pdf

Also some hints elsewhere that lasers are useful but very expensive for the purpose at present.

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kiwirock

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Ultimate Geek

#1826865 22-Jul-2017 04:32

There's not a lot you could do. If you were turning the wheel - take note if the car is turning or not. If not, back off the brakes if at all, move your thumbs or fingers out from inside the steering wheel so you don't end up braking fingers or a hand if the vehicle is going to roll or run over really bad terrain, and go easy on the brakes, if at all.

In 2 seconds there's really no way to save it on black ice other than not lock the wheels to the point you can't steer.

I've been through to Milford quite a few times as I live down south. I've been through with snow on the sides of the road at least 2-3 times higher than the vehicle at Homer tunnel, then down that brilliant zig zag road on the other side where it's very steep. Some of that road is extremely dangerous in winter, no matter the driver.

Once you hit the forested area passed Te Anau downs, that never sees the light of day on some of those corners due to tree top canopies.

I tackled the zig zag slower than a walking pace and a higher gear (snow mode was forced 2nd) with the RPM's close to 1,000 or less so there was less compression on the driveline. Then made sure I planned a path as straight as possible through the corner so I could see where I was going to end up. If I could see around the corner and down the road, I have no problem crossing the centre line where the camber isn't on your side with ice.

Sometimes you just can't judge until it's to late when you're already on it. As you found out.

Sometimes even trying to get a feel for the road doesn't work. Tap the brakes before coming up to a corner and hope if there is ice there it'll let you know before you go to corner. But you don't truly know until you're on it.

Try to never out drive your stopping distance, and never assume the road is safe when it's near freezing outside. Also pay attention to the road finish... worn or slick rather than lots of stones to bite and try to avoid the worn area where everyone else before you has driven if it feels very cold outside.

Every mm might count in this situation, so maybe a few pounds of air out of the tires may have made a difference. Tread pattern and how much in contact with the road (studded being the best on top of this), and modulating braking is the only thing that counts. Sometimes it's just not enough.

Maybe car manufacturers will put a small sanding unit on cars one day for ice driving in cold climates during winter. I don't see why it would hurt.

Greendrake

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Master Geek

#1827873 23-Jul-2017 20:01

Can't update my original post anymore so adding this here. Today I went to the crash site to take pictures of the road layout. And now I know how exactly the skidding started. It was the bridge! You know, when you enter and exit a bridge, you are bumped up a little bit. These bumps (perhaps, mostly the exit one) were what took the grip away!

tdgeek

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#1827891 23-Jul-2017 20:06

Thanks for the effort for the pics

Yes, if its bump bump, that loses traction, then when the tyres get back to the black stuff, there is a lot of erratic momentum.

andrewNZ

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#1827946 23-Jul-2017 21:09

Actually also as likely, because bridges are open below, they cool faster and are the first/worst places for ice to form in my totally non expert experience.

gzt

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#1827947 23-Jul-2017 21:12

Possibly a good place for those little lights if they are any good.

Edit: or a different surface

kiwirock

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Ultimate Geek

#1827949 23-Jul-2017 21:14

Looks like ABS stayed on. No sign of the wheels pushing the gravel up in front of the tires on the side of the road. That would suggest to much speed When you came off the road. The handbrake may have helped dig in to the gravel when it came off the road. You can see it gets no sun but the approach path of your vehicle doesn't give away the frosty ground much. The exit angle shows it could be quite slick. Looks like there was a fair amount of grit there to. That in its self is just as bad if wheels are locked up. ABS usually doesn't quit until below 20. So I'm guessing we'll above this when you came off the road. All you can do in winter at Milford is come to a crawl on corners near snow the snow line. You want to be ready to not brake basically at corners.

Greendrake

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Master Geek

#1827960 23-Jul-2017 21:35

kiwirock: Looks like ABS stayed on. No sign of the wheels pushing the gravel up in front of the tires on the side of the road.

The path from the tyres was pretty much visible the next day (15 July) when I went there in a tow truck to recover the vehicle. Sadly my phone battery was flat at that time. Road workers were already there too. Since then they've put the first of the 3 arrow signs back (I smashed the first one off).

andrewNZ

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#1827962 23-Jul-2017 21:42

Now I look harder, I think you'd have been better off if you lifted off the brakes and kept the wheels rolling. It looks like it must have bitten for a bit.

Either way, there's no arguing with instinct in the moment. You're safe and well and that's the best outcome there is.

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