Hydroplaning risk rises with speed and shallow water but drops past 10 mm, study finds - Automotive

The Federal Highway Administration estimates that wet pavement and severe weather contribute to around 500,000 injuries and 6,000 deaths each year. Credit: Andrew Davis Tucker/UGA

As summer approaches, you might be planning a road trip. A recent study from the University of Georgia explores how you can stay safe while driving in the rain. Vehicles can hydroplane when water gathers on a road, causing tires to lose their grip.

UGA researchers used both a computer and a live simulation of tires on a wet road to explore the different factors that contribute to hydroplaning. Speed and water thickness both increased the chance of hydroplaning, but the risk fell once the water was about 10 millimeters (0.4 inch) deep. The paper is published in the journal Applied Sciences.

The Federal Highway Administration estimates that wet pavement and severe weather contribute to around 500,000 injuries and 6,000 deaths each year.

"This is a very important safety issue," said Linbing Wang, corresponding author of the study and a professor in the UGA College of Engineering. "If we have a good understanding of what the contributing factors are, then we can improve them, either through the design of pavements or the vehicle design, helping to save lives."

Water depth on roads contributes to hydroplaning risk—to a point

The researchers used field tests to simulate rainy conditions on a road. Tires were placed in a mechanism that allowed the researchers to adjust tire speed and add water onto the pavement. The researchers then placed sensors along the track. As the tires moved through the water-soaked pavement, those sensors measured the forces that contribute to hydroplaning.

At first, as water depth increased, the risk of hydroplaning went up. However, once the water reached about 10 millimeters (0.4 inch) deep, the risk of hydroplaning steadily fell. This could be because thinner layers of water are harder for your tires to break through, making it more difficult for them to stay on the road.

For deeper water, the risk of hydroplaning is highest when your tires first hit the wet pavement because it's before your tires can disperse the water. As the water is pushed away by the tires, the risk of hydroplaning goes down.

Higher speeds likely contribute to hydroplaning risk

Speed was also one of the most impactful risk factors when the road surface conditions were the same between tests, the researchers said. As tires move faster, the water on the track puts more pressure on them, lifting them off the road.

"It's very similar to an airplane. You reach a certain speed, and the vehicle lifts," Wang said.

The tread patterns of the tires, tire pressure, surface texture of the road and whether water can drain from the road also play a role in hydroplaning risk, the researchers said.

Slower speed, car maintenance can prevent hydroplaning

Driving slower in rainy weather can drastically reduce the risk of hydroplaning, the researchers said. Replacing worn tires is also critical.

A good surface texture on the road and infrastructure changes could also help keep drivers safer. Georgia, for example, is among the best at applying a thin surface layer of pavement onto highways that allows water to drain through the asphalt rather than pool on roads.

"Speed is something that drivers can control. The pavement texture and raining thickness you cannot control," Wang said. "Human factors affect safety. That's something we should all be concerned about." 

Provided by University of Georgia 

by Sydney Barrilleaux, University of Georgia

edited by Gaby Clark, reviewed by Robert Egan 

Source: Hydroplaning risk rises with speed and shallow water but drops past 10 mm, study finds