It's perhaps surprising, but true: Driving on a rainy day is more dangerous than driving on a snowy one. When the rain starts to fall and pavement is wet, your likelihood of a crash is higher than during wintry conditions like snow, sleet and ice, according to data from the National Highway Traffic Safety Administration (NHTSA).
After averaging 10 years of statistics, NHTSA researchers found that 46 percent of weather-related crashes happened during rainfall, but just 17 percent while it was snowing or sleeting. Those statistics are partially explained, of course, by the fact that many drivers have the good sense to stay home during a bad snowstorm, says Debbie Hersman, president and CEO of the National Safety Council, which offers defensive driving courses. But the statistics also reflect a sobering truth, she says: Drivers often do not respect the rain, and fail to adjust their driving habits to hazardous conditions.
Here is how to reduce the chances of being a rainy day statistic, according to safety experts.
Get Your Car Rain-Ready: Tire tread is key, says Bill Van Tassel, Ph.D., manager of driver training programs for the AAA national office in Orlando, Florida. Dig out a quarter (forget the old advice about Lincoln's head on a penny, as some researchers have found the quarter test more accurate). Insert it upside down into your tire tread. "If part of Washington's head is always covered by the tread, your tires have more than 4/32 of an inch of tread remaining. If the top of Washington's head is exposed at any point, you should replace the tires."
According to NHTSA, tires with 2/32 of an inch of tread are unsafe. However, you may want to replace tires before they get this worn, depending on driving conditions.
Slow down: Driving too fast for conditions is especially dangerous on wet pavement because your tires lose traction with the precipitation, Van Tassel says. "When roadways are wet, the friction is reduced between the tire and the road,'' Hersman adds. No friction is a bad thing. Tires are meant to grip the roads, not slide on them.
How much does traction decline in wet weather? "You might lose about one-third of your traction," Van Tassel says. And that figure is why this recommendation makes sense: Reduce your speed by about a third when it's wet or rainy. If the speed limit is 55 mph, aim for under 40 mph. "That is not a hard statistic but a rule of thumb," he says.
Back off: Forget the old rule about keeping a certain number of car lengths between you and the vehicle in front of you, Van Tassel says. Focus on staying 3-4 seconds behind the vehicle in front of you in dry conditions. Watch the vehicle in front of you as it passes a fixed marker, such as a street light, he says. Then count 3 seconds. Add more time if it's raining, staying about 5 seconds behind.
For each additional driving challenge, add another second, Van Tassel says. If it's raining and you are driving at night, you should aim to be 6 seconds behind the vehicle in front of you.
If possible — and in heavy traffic, it might not always be — try to keep from being boxed in by cars in the lanes on either side of you, Van Tassel says. If you have space on either side of your car, you have an easy out in case the vehicle ahead of you stops suddenly.
Know when to lean on technology, and when not to: "While some technologies are not advisable for use during bad weather, others can help," Hersman says. Do not depend on cruise control, adaptive cruise control or forward collision warning systems during the rain, she says. Wet weather may affect the systems' sensors and reduce their reliability, she says.
Even adaptive cruise control, which is an advanced version of cruise control and maintains a set speed and a safe following distance, is not recommended during rainy weather, Van Tassel says.
Here's why: When you're driving without cruise control and you see a hazard, you lift your foot off the gas pedal as you prepare to brake. As you come off the gas, the nose of the car starts to dip a bit, transferring some weight to the front. This provides more traction on the front tires. But if you have cruise control on, your speed remains constant after you lift off the gas. There is no dip. You lose that helpful early weight transfer.
On the other hand, a traction-control feature is tailor-made for rainy days. "It prevents the wheels from slipping on wet pavement and helps the driver maintain control when stopping or accelerating in the rain," Hersman says.
Antilock braking systems (ABS) are meant to prevent the loss of steering control during hard braking, particularly on wet and slippery roads. ABS is a component of electronic stability control (ESC), which has been required on new cars beginning with the 2012 model year. Electronic stability control, which helps stabilize your vehicle when it starts to veer off the intended path, can be valuable in wet weather as well, Hersman says.
Van Tassel sees anti-skid control and lane-keeping assist features as being potentially useful in the rain. "Anti-skid control is a bit more advanced than traction control," he says. "Traction control helps prevent the drive wheels from spinning when you apply the gas (as when trying to get a car moving from a stop in snow or ice). Anti-skid control actually helps prevent front-wheel or rear-wheel skids when you are driving through a turn (regardless of whether the surface is dry or slick)."
However, like other technology features, these should be viewed as a backup, he says. The best advice for a rainy day when it comes to advanced vehicle technologies is to "just pretend they are not there," he says.
When You Hydroplane
Suppose your car hydroplanes, which can be a terrifying experience. Hydroplaning happens when the tires are riding on the top of a layer of water and have completely lost contact with the pavement. It can happen when your speed is as little as 35 mph. You will know when it happens. "Steering will get light in your hands," Van Tassel says.
"Gently ease your foot off the gas," he advises. "This may transfer enough weight forward so that your front tires regain contact with the road."
If not, he says, gently squeeze your brakes to slow the vehicle down and transfer weight to the front tires. Steering will not really be possible, since the tires are riding on a film of water.
"We don't recommend turning the wheel in a hydroplaning situation," he says. "If you have some steering 'dialed in' when the front tires finally do regain traction, you might immediately steer right off the road. Obviously, that's not a good thing."
If you do start to skid, don't turn into the skid, regardless of what you've heard. "Continue to look and steer where you want to go," Van Tassel says. This strategy works for both front and rear skids.
Getting Comfortable With Scary Situations
Some wet-weather driving emergencies can be handled by an application of common sense. Others require something more, such as practicing driving techniques that can save your life. Consider taking an advanced driving training class. But whatever else you do, begin with the simplest life-saver of all: Slow down when the rain starts to fall.
