The deaths of four family members, including two young children, whose sport utility vehicle skidded on a rain-soaked North Carolina highway this week and plunged into a ditch are drawing attention to the risks of driving in wet weather.
"Witnesses told us that the vehicle did a 360[-degree turn] before it ran off the right side of the road," Sgt. Kenneth Pitts said. "In downpours like this, especially when you've got ponding water and all, it is just imperative to have tires that are safe. That was a large, large factor in this tragedy."
The lone survivor, a 3-year-old twin of one of the children killed, currently is fighting for his life, authorities said.
Hydroplaning occurs when there's too much water on the road for tires to disperse. A wedge of water forms in front of the tires and the car rides onto that wave, losing contact with the road.
Adequate tire tread thickness helps wick water away. Experts at the Consumer Reports test track say that there needs to be at least one-16th of an inch of tire tread -- enough to reach President Lincoln's head on a penny -- for the water to escape.
"The main reason why people hydroplane is they drive too fast for the conditions," said David Champion of Consumer Reports. "When it is really wet, people don't think they need to slow down. If it is raining and if it is raining heavily, slow down."
Another cause of hydroplaning is worn tires, Champion said. When a car's tires begin to wear down, they should be replaced.
"All tires will hydroplane at some speed," he said. "But the better the tires, the more treads you have. ... And the less likely you are going to hydroplane."
Stay Calm and Drive Slow
It also is important to maintain a car's required tire pressure, he said.
In wet conditions, drivers should slow down to 30 mph or less, avoid hard braking and sharp turning and try to drive in the tracks of the vehicle ahead of them. He said to watch for water puddles on the road and wet road conditions.
"If you are going into a dip in the road, there is likely to be water on the bottom," he said. "If you see a car in front [of you] all of a sudden have a big splash of water out to the side, slow down, because you are going to be hitting that."
Consumer Reports experts said that if a car starts to hydroplane, a driver should take his foot off the gas, steer in the direction he wants to go once they regain traction and not slam on the brakes.
Champion said one of the most important things a driver should do is not react quickly.
"If you lock up the tire when you are sliding on the surface of the water, when you actually hit the road you could slide out of control," he said. "Lift off the gas, steer straight until the tires are contacting the road. Then you can make your steering maneuvers, your braking to slow down and get you into a safe place."
ABC News' Elisabeth Leamy contributed to this article.