Transportation Science

What happens when a car hydroplanes?
Answered by Science Channel
  • Science Channel

    Science Channel

  1. When a car drives through water, it might lift off the ground if the water doesn't splash away quickly enough, causing the car to, in essence, glide off the water and lose traction. That's called hydroplaning. The water at the tires' fronts builds up faster than the car's weight can displace it. It's water pressure inside the tires' grooves that makes the entire car rise up slightly and slide along on a minute layer of water between the tires' edges and the ground.

    Special tires with deep grooves going in the same direction as the tread give water a route to get out from under a car, providing extra traction and reducing the possibility of hydroplaning.

    NASA has completed extensive research on the conditions that work together to cause hydroplaning of automobile or aircraft tires. It was precipitated by a number of crashes of military aircraft on wet runways. In fact, as far back as 1957, tire treadmill tests demonstrated hydroplaning [source: NASA]. Understanding hydrodynamic principles of hydroplaning has helped improve tire design over the years for better overall traction and water displacement.

    Hydroplaning still occurs, however, and is not the same as skidding. The feeling that the car is out of control or lifted off of the pavement is a frightening one for drivers -- and it should be. Properly inflated tires and intact treads help minimize the chance of hydroplaning, so keeping tires inflated and replacing them when the treads wear are important safety measures.

    If you get caught hydroplaning, don't brake or jerk the steering wheel suddenly; these actions might just cause a dangerous skid. Ease your foot off the gas until the car slows down and you feel the road under your tires again [source:]. One tip that you might have heard about is to turn off cruise control when driving at higher speeds on wet roads. The reason is that you need to respond quickly to reduce power to your car's wheels, and it takes a little longer to do that with cruise control, which maintains a steady speed, no matter the outside conditions [source:]. And it's always better to slow down in wet weather.

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