Road beat: ‘Four-wheel drive doesn’t negate laws of physics’
By Larry Weitzman
“Seventy-five percent of the accidents in snowy conditions are four-wheel drive vehicles” said Lee Aderlee, retired California Highway Patrol officer. That’s a telling statistic that all drivers of four-wheel drive vehicles should be aware of.
Aderlee went on to say, “Four-wheel drives don’t negate the laws of physics.”
“Many people who drive four-wheel drive vehicles develop a false sense of security and get themselves into trouble … four-wheel drives will not stop any faster than a two-wheel drive car,” Aderlee said. “Four-wheel drive cars accelerate better, but very few accidents occur when accelerating, they occur when they are going too fast for the conditions and are unable to slow down, steer and/or stop.”
Aderlee is absolutely correct.
A four-wheel drive is just what it says. With limited slip differentials, it can put torque or power to any or all of your vehicle’s wheels. Most cars today are front-wheel drives which means the drive wheels are only on the front axles. There is no power to the rear wheels. Rear-wheel drive is the opposite.
In four-wheel drives, if the rear wheels cannot obtain sufficient traction to accelerate the vehicle, then power is transferred to the front wheels or spreads the power to all wheels to obtain the necessary traction. With front wheel biased four-wheel drives, most power goes to the front wheels unless slippage is detected.
But four-wheel drive only helps in making you go in a straight line, it does nothing to help you stop and once front traction is lost, you have no effective steering. The only devise that helps you stop and maintain directional control are antilock brakes. In addition to ABS are electronic black boxes called stability control, which through throttle retardation, individual wheel braking, accelerometers, yaw sensors and steering input sensors attempt to keep the vehicle going in the intended direction. All of these new things should never lull you into as put by Aderlee “a false sense of security.”
Aderlee says there are two things to keep in mind when driving in snowy conditions, speed and anticipation. Any speed beyond the ability to react safely to a problem, such as another vehicle out of control, an animal or a road obstruction is too fast. Four-wheel drive will not help you in such a situation.
Aderlee says chains offer the most effective stopping action as well as significantly improved traction.
Four-wheel drive will help keep you going in mud or in slippery conditions, but it doesn’t remove the common sense necessary when driving in snowy or icy conditions.
When you see all those advertisements of four-wheel drive vehicles doing amazing things, there is a captioned which usually reads: “Professional driver on a closed course.” But even more important is that those professional drivers are in perfect conditions with the knowledge of anticipation. And as the advertisement says, they are professional drivers, drivers highly skilled and experienced in negotiating difficult conditions and who understand and can feel what the vehicle is doing. How successful would an off the street driver be in a NASCAR race? Most of the time all you do is turn left. How hard can that be? At the speeds they travel, extremely hard.
It’s fairly easy to go straight during snowy conditions. It’s when you need to slow down or alter your direction when you get into trouble. When that happens, and that can happen at any time, a four-wheel drive has no advantage over a comparably equipped two-wheel drive. Drive within your limits, the weather’s limits, the road condition’s limits and your vehicle’s limits. The braking ability of a four-wheel drive vehicle is no better than a two-wheel drive vehicle. A two-wheel drive vehicle with ABS and/or chains will outperform a 4 x 4 in braking during snowy conditions without ABS and/or chains.
When the CHP posts speed limits of 25 mph with chains, it’s a maximum safe speed. They are not kidding. The laws of physics are not repealed by four-wheel drive. When traction between the rubber and the road is reduced, so must the speed, as stopping distances are increase by the approximate square of the speed under the best of conditions.
Larry Weitzman has been into cars since he was 5 years old. At 8 he could recite from memory the hp of every car made in the U.S. He has put in thousands of laps on racetracks all over the Western United States.
Larry Weitzman, Good article on four wheel drive vehicles. They are great in snow and ice as long as you use some common sense and know the vehicles limits and your own driving capabilties.
I always used to laugh at the drivers stuck in the middle berm in the center lane of hwy 50. Trying to cross an incredibly high amount of snow and the vehicle is all high centered with spinning tires getting no traction.
Although we have’nt had to worry about too much snow or berms in sometime . It seems even with a light snowfall we still have alot of accidents in the Sierras due to winter driving conditions .
Happy motoring! , OLS
OLS- I agree it is funny to see all the cars high centered on berms in Kings Beach too! The car manufacturers continue to advertise “the miracle” of being able to speed as well as cut through snow. Common sense gets left on the showroom floor
What is the % of cars on the road in snowy conditions, 75% ?.
Some years ago a friend of mine on the local police department did an informal (and unofficial) survey of several years of winter driving accidents in South Lake Tahoe with the finding that far more winter accidents involved and were caused by local drivers.
Perhaps the white knuckled fear of the visitors trumps the casual confidence of the locals on a snowy day.
What is the # of 4 WD on the road in snowy conditions? If it’s 75% then it’s a wash.
seems that sometimes 4WD does negate the laws of common sense!
OLS,
I’ll have to agree, “vehicle is all high centered with spinning tires getting no traction”
I’ll take my 4wd over some crappy little Awd that has low ground clearance hands down !!
I recall fond memories of Hwy 50 as a parking lot from Echo to Stateline and all passes except 89 to Alpine closed. What many of us found out is if you run studded tires and 4wd it makes a huge difference, though I have seen a number of pine trees that chased people all over the place in snow and some other times I remember not being able to see the road signs at all, but that is a distant memory now.
‘What is the # of 4 WD on the road in snowy conditions? If it’s 75% then it’s a wash.’
That doesn’t counter physics.
A vehicle with blizzaks has more stopping and turning traction than any AWD/4WD with any other tire. My ABS only kicks in in the worst conditions and even then it only last for 1 second at most. I can’t rotate my car beyond 90 degrees with a good e-brake turn. I’ve tried, the wheels will probably get pulled off of the rims before my car spins.
And the shady insurance companies still won’t give a discount for protecting myself and others with the best tires.
Lou,
You are overthinking what the CHP said;
he said that 3/4 or 75% of the accidents in snowy conditions involve 4 wheel drive vehicles.
It has nothing to do with the number of cars on the road…..in 100 accidents, only 25 are NOT 4 wheel drive.
I agree that in bad weather there may be more 4WD cars on the road, but it is the number that get into accidents that is the point.
It clearly shows that many people do not understand that 4 wheel drive is not a magic bullet that keeps you safe. You need to understand the physics and not overdrive your own skills or the capability of the vehicle you are driving.
Duke-
If you can’t do an e brake turn beyond 90 degrees you are doing it wrong, or you are not going fast enough for the traction conditions at the time.
Ever driven on blizzaks? Stupid name, not cheap, great tires. They are probably cheap right now. The WS 50s were better but the new compound lasts longer.
@duke of prunes: You really have a handbrake? Is your car stock? What are Blizzaks? Can you post a link? Thanks.