Aquaplaning – When the Car Loses Traction on Wet Roads
When high speeds and standing water on the road come together, it can have serious consequences for drivers. Due to the wet road surface, it is possible for the car to start hydroplaning, and the driver loses control of the vehicle. This phenomenon, known as “aquaplaning” or “hydroplaning,” can occur during heavy rain and poses a significant risk of accidents.
During aquaplaning, the vehicle suddenly and without warning loses traction on the road and instead glides on the layer of water. Since there is very little or no tire contact with the road in this situation, neither steering nor braking can provide a remedy. Attempted corrective maneuvers can even lead to severe accidents if the vehicle suddenly regains traction on the road in an unfavorable position.
Ideally, one should completely avoid aquaplaning, but it’s essential to be prepared for it if it occurs.
What is Aquaplaning?
Especially in the autumn, heavy rainfall can lead to the accumulation of water on the road. Normally, the tires displace the water on the road, with some splashing to the sides, and the tire tread channels the remaining water away, allowing the tire’s contact with the road to be maintained.
However, when there is an excessive amount of water on the road or the vehicle is traveling at too high a speed, the tires may no longer be able to displace the water under control. Instead, the tires push the water ahead of them, creating a kind of water wedge. This water wedge wedges itself between the tires and the road surface. In the worst case, the car loses traction completely and begins to skid or hydroplane. Without contact with the road, it cannot be brought back under control solely through steering or braking.
When Does Aquaplaning Occur?
The causes of aquaplaning are not always the same. The main ingredients are, of course, rain and wet conditions. Additionally, the road’s surface also plays a role. Aquaplaning occurs more frequently on roads with depressions or ruts. In depressions, water collects and may not drain away, and if it’s deep enough, it cannot be displaced by tires. However, when heavy rain occurs, aquaplaning can also happen on a road without defects.
The type of road is only somewhat relevant to aquaplaning. The driving speed is a significant factor because higher speeds increase the likelihood of aquaplaning.
When assessing the risk of aquaplaning, it’s important to rely on your instincts as well. If you feel like the car is “floating” on the road, you should gradually reduce your driving speed without sudden braking. Additionally, if the tires start spinning on the road markings, it can indicate the onset of aquaplaning.
What Factors Favor Aquaplaning?
Water Depth: The deeper the water on the road, the greater the likelihood of aquaplaning. Furthermore, the road surface influences how well water can drain away. Rainwater tends to accumulate particularly under bridges, in curves, or in depressions, which can become a hazard. The thicker the layer of water on the road, the lower the maximum speed at which the tires can still maintain traction on the surface.
Speed: Speeding in wet conditions can have fatal consequences. Just like with increasing water volume, the likelihood of aquaplaning also increases with higher speeds in rainy conditions. An elevated risk begins at around 80 km/h.
The maximum speed at which the tires still maintain sufficient contact with the road is called “aquaplaning speed.” The ADAC tire test indicates a maximum speed of 75 to 85 km/h for tires with a tread depth of approximately 8 mm and a water depth of 7 mm. Often, the amount of water on the road can exceed the tested 7 mm, according to ADAC. Additionally, the test assumes new tires, which may not be the norm. Therefore, ADAC recommends not exceeding a speed of 80 km/h in heavy rain.
Tire Width: Wider tires must displace more water than narrow tires. Consequently, wider tires are generally more susceptible to aquaplaning and sliding. Tire manufacturers attempt to compensate for this through the design of the tire tread. Special tread patterns and contours can make wider tires less prone to sliding and losing contact with the road.
Tread Depth: In addition to tire width, tread depth also plays a role. The tread grooves in the tire allow water to drain, ensuring that the tire maintains contact with the road even in wet conditions. The deeper the tire’s tread, the more water can be drained. Over time, tires lose tread depth, providing progressively less protection against aquaplaning. Even in relatively light wet conditions, aquaplaning can occur with low tread depth and high speed.
Tire Pressure: Tire pressure also plays a role when it comes to aquaplaning. Tires are more prone to losing contact with the road when tire pressure is low. Low pressure increases the contact area between the tires and the road. With a larger contact area, similar to wider tires, there is more water that needs to be displaced. Additionally, due to the low pressure, water can more easily get under the tires, and less water is pushed aside. Tread depth and tire pressure should, therefore, be regularly checked.
Road Surface: Lastly, the condition of the road also significantly affects the risk of aquaplaning. Since speed is a crucial factor, aquaplaning mainly occurs on roads where higher speeds are traditionally driven—especially on multi-lane roads and highways. The risk tends to be lower on rough road surfaces. While irregularities like depressions and grooves promote water accumulation, the inclination of the road has a positive influence. The steeper the slope, the better water can drain.
Other factors include the weight of the vehicle and the condition of the shock absorbers. Vehicle weight is also relevant in relation to tire pressure. Depending on how heavily the car is loaded, tire pressure needs to be adjusted. Outdated shock absorbers can also contribute to aquaplaning.
How to Avoid Aquaplaning?
Aquaplaning can be best prevented by adjusting your driving to the weather and road conditions. In wet conditions, it’s essential to reduce your speed. The worse the weather, the slower and more cautious you should drive. This includes driving outside of tire tracks if necessary and paying attention to signs warning of hazards.
Furthermore, every driver should monitor the condition of their vehicle. Tread depth and tire pressure should be checked regularly, and worn-out tires should be replaced promptly. If this is not possible immediately, the additional risk should be compensated for by driving particularly cautiously.
What to Do When Aquaplaning Occurs?
If, despite all precautions, the car starts to skid, it’s essential to know what to do. Here are some important guidelines:
- Avoid strong braking
- Hold the steering wheel with both hands
- Avoid rapid steering movements
- Gently release your foot from the accelerator pedal
- Depress the clutch
- Gradually reduce speed
When the vehicle loses contact with the road, neither steering nor braking will have any effect. If the tires regain traction on the road, abrupt maneuvers can lead to severe accidents. The vehicle can skid and spin out of control.
That’s why “less is more” when it comes to aquaplaning. The smoother the transition from water back to asphalt, the better you can regain control of the vehicle afterward.
Adapt your driving behavior to the weather. This means driving cautiously and attentively, and reducing your driving speed in wet conditions. Regularly check your vehicle and tires and replace outdated parts as needed.
If you still find your car skidding, try to avoid panic and hasty maneuvers as much as possible.