We’ve all experienced hydroplaning (aka aquaplaning). That’s when your front tires lose traction, and therefore both steering and braking, on a wet surface. It feels like skating on ice and can have similar bad results–very scary, sometimes disastrous. But unlike sliding on ice or snow, which we usually can anticipate and deal with in those conditions, hydroplaning can happen almost anywhere at any time at any temperature when there is water on the road.

Hydroplaning happens when a rotating tire floats up and skates on the surface of the water. It’s a function of vehicle speed, the tire’s tread depth (and design) and the depth of the water, and your only way to regain traction when it happens is to back off and slow until the tire stops skating and drops through the water to recontact the pavement. Until you do, you’re an unguided missile.

Most experienced drivers–if they are paying attention–can feel the loss of traction when their steering wheel goes loose, and most instinctively back off to regain it. But mostly for less experienced, and distracted and (increasingly) automated drivers, technology supplier Continental is working on a sensor-based system to warn drivers of hydroplaning conditions. And to warn other cars and drivers in the area through vehicle-to-vehicle communications.

Aid in recognizing traction loss

“The system is not intended to replace the driver but rather enhance his/her senses,” says Ibro Muharemovic, head of engineering systems, ADAS, Continental North America. “Some trained drivers are able to recognize the slip and handle it correctly. However, most tend to recognize the slip too late and then try to steer, especially in a moment of panic. And that steering input causes a problem as soon as the wheel catches traction again. Our system provides the driver with a ‘heads up’ warning quicker and sends a warning to other drivers approaching the same location.”

The system under development uses tire-mounted sensors, surround-view cameras, algorithms and brake actuation to give drivers time to prevent front-wheel floating while warning other drivers to be prepared. It uses signals from the cameras and tire-mounted electronic-Tire Information System (eTIS) sensors to detect a possible hydroplane situation as early as possible to trigger an early warning to the driver. And simultaneously to enhance control and stabilization of a vehicle hydroplaning by creating a torque-vectoring effect through individual rear-wheel braking.

To detect hydroplaning situations, video images from surround-view cameras mounted in the side mirrors, in the grill and on the rear of a vehicle are analyzed. Excessive water displacement in all directions is a characteristic sign of hydroplaning. “These camera images show a specific splash and spray pattern that can be detected as hydroplaning in its early phase,” Muharemovic explains.

Using tire input

The system also uses accelerometer signals from Continental’s eTIS sensors, mounted on the tire’s inner liner, to detect hydroplaning risk. On a wet road, when enough water is transported out of the tread to ensure an appropriate grip, the signal shows a distinct pattern. But as soon as a wedge of water begins to form in front of the tire footprint, the acceleration signal indicates an early risk of hydroplaning. Since the eTIS sensor can also read the remaining depth of the tire tread, a safe speed for a given wet road condition can be calculated and communicated to the driver.

“Wet road conditions are difficult for a driver to evaluate,” he says. “Once you feel your vehicle floating, it may be too late. Our hydroplaning assistance concepts detect the early hydroplaning phase to make the driver aware of what is going on under the tires. This can help drivers or automated vehicles adapt their speed appropriately to wet road conditions.”

Since hydroplaning depends on tread depth, the depth of water on the road and speed, Continental recommends renewing tires with three millimeters (0.11 inch) of residual tread depth because the risk of hydroplaning increases significantly below that level. “This is one of the last blank spots on the strategic map towards greater road safety,” adds Muharemovic. “But drivers must continue to adjust their speed to wet roads and keep an eye on the tire’s tread depth.”

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