Friday, December 12, 2008

Winter Driving

Today while I was trying to get a 12 pitch roof going the temperature plummeted and it started snowing and blowing. This job is about 20 miles up the freeway in NE Oregon running around 3000 feet elevation, roads get real iffy pretty quick. About half way home there was a Jeep SUV in the media up right but with the roof crushed and two state police cars and an ambulance. Heading toward the wreck closer to town were five sheriff's cars and another ambulance, that's a lot of attention for a one car wreck indicating a fatality or real serious injuries. There is nothing unusual about winter wrecks on the freeway around here, we get lots.

Let's start with something pretty simple as a concept, when the roads are crummy and you drive fast to cut time you need to recognize that being in a ditch or an ambulance is going to add significantly to your trip time. Depending on your vehicle and equipment there is a safe speed to travel and it is wise to recognize that marginal conditions can quickly turn drastically bad.

Vehicle types lead to a lot of over confidence, the fact that it can go doesn't mean it can stop or steer, that SUV or front wheel drive may get going and stay going but that isn't the whole equation. If the darn thing can't stick to the road for steering, slowing, or stopping the fact that it could get going fast only means problems. Chains, studs, or specialty snow and ice tires will help keep the thing where you need to to be, not your "all weather radials." Whatever your capabilities you have to assume stupidity on the part of other drivers and allow for it.

You have to realize that some time something is going to go wrong out there and you'll have to deal with it. Over-steering or over-corrections lead to most single vehicle mishaps. Gentle is the rule and a scrape on a guardrail or stuck in the median or the side of the road trumps going upside down or tangling with other vehicles. You may really not want to mark up that paint job but reefing on the steering wheel will lead to disaster.

Your brake pedal is not your friend if you're losing control, brake systems put most stopping power to the front wheels and going to the brake will accentuate whatever else is going wrong. If the front isn't steering, going to the brake will simply cause it to slide worse and if the back end is trying to go around you'll get loopty loops, a bad thing. If you go into a slippery curve too fast hitting the brakes will pretty much ensure you'll not turn, sliding tires do not steer.

There are other issues involving the end that drives the tires, front wheel drive is completely different from rear wheel drive and four wheel drive is neither. Lifting off the throttle slows the tires, this may or may not be in your favor. If the back end of a front wheel drive car is coming around slowing the front tires will accelerate the rear drift. There are only two things that will get the back into line with a front drive vehicle, either throttle up or go to the hand brake. Accelerating is the more controllable method but circumstances may prevent that in which case the emergency brake will slow the rear, in which case the brake needs to be modulated, if it is a hand brake (most likely today) you need to hold the release while gently slowing the rear tires with varying pressure.

Rear wheel drive vehicles will respond to throttle downs if the back is coming around, though automatic transmissions will do so gently and possibly too slowly in which case a down shift will help if you aren't going too fast for the next gear down to not break the tires loose. Down shifts are tricky and not knowing what is going on with it could be bad. With rear wheel drive it is pretty rare for going to the gas to be of help. In matters of control in bad conditions rear wheel drive is easier to deal with although it is not as desirable for getting going; you generally get more warning with two wheel drive that you are pushing conditions.

Four wheel drive brings the worst of either front or rear wheel drive into play if the vehicle is getting out of shape. All tires react to throttle changes so throttling down will probably mean an accentuation of the problem of which ever end is having difficulties. Four wheel drives tend to have a higher center of gravity which means that in a sideways slide will very possibly result in a roll-over if rough or soft ground is encountered while in that condition. It is most likely in a four wheel drive that throttling up will help most, the problem is that if you're in trouble you probably were already going too fast.

There are some hidden dangers in winter driving, over passes freeze much sooner than road way does, and in bright sun will thaw and then freeze sooner because it lacks the heat sink of the earth. In sunny weather road ways thaw and if that area becomes shaded at low temperature it will freeze while the rest of the road is not icy. This condition is most common in hilly or mountainous country and that tends to mean curves and solid objects. Paying attention is much better than trying to rescue the situation. Fog and very light rain are prone to creating ice when temperatures are low, and the nasty part is that it is black ice which looks very much like wet road way.

The best way to avoid having to rescue a situation is to not get into it in the first place, if you have winter conditions to drive in; have traction devices and drive at a prudent speed. Know how to drive in that kind of weather, if you're unfamiliar find a large vacant parking lot with those conditions and try it out. Park the vehicle and spend a night in a motel, it is cheaper than smashing up a vehicle and you can never get back the time spent in a hospital or worse - dead. I will assure you that people will die on the Interstate within ten miles of my town because of winter driving conditions, they do every year and it is a sad waste brought on by ignorance and impatience. Don't be one, here or there.


Phil said...

Excellent advice, Chuck. Slippery pavement is precisely why I hate automatic transmissions and dearly love 4- 5- or 6-speed manual transmissions.

Advanced driving techniques such as double-clutch downshifting, trail-braking, feathering brake and throttle, and driving ahead of oneself are probably lost on most drivers who lack significant track time or truck driving experience, and nuanced terminology such as understeer, oversteer, drop-throttle oversteer, weight transfer, and balance further confuse the issue.

You've done a superb job of covering the basics of driving in winter conditions; the only things I could add are that locking up the wheels (unless done intentionally for short-term effect) is a no-no, and that drivers should looks as far down the road as possible while remaining alert to what might be overtaking them; if you don't see trouble coming well in advance, you have almost no chance of avoiding it when driving in slippery conditions.

Chuck Butcher said...

I grew up in snowy and icy winter conditions and drove some pretty high power vehicles w/manual trannies, I really tried to keep it simple.