A car aquaplanes through water

In last week’s post we included some pointers for staying safe when driving through the stormy weather which Britain has been experiencing lately. Whilst 70 mph gales, waves breaking over flood defences and falling trees are all dangers to be aware of, we thought it was worth focusing in on one factor which can affect drivers facing “normal” rainfall as well as extreme weather.

What is Aquaplaning?

“Aquaplaning: verb- UK / US: hydroplaning: a situation in which a vehicle slides out of control on a wet road”

Whilst this Oxford English Dictionary definition tells us a good overall meaning of the term, it doesn’t help to understand how it happens and what to do if it does.

What Happens when a Car Aquaplanes?

In normal, wet conditions, as a car travels along the water forms a wave in front of each tyre and moves around it. This is because the pressure of the tyre on the road is greater than the pressure of the water beneath it. The treads also help to keep the tyres in contact with the surface of the road, by funnelling the water away from the rubber connecting with the road.

When the water on the road reaches a great enough depth, particularly if there has been a sudden storm without enough time for the water to drain away, the pressure of the water pushing up underneath the tyre can exceed that of the tyre pushing down. This prevents the tyre from being able to displace the water and lifts the car off the surface of the road. In some conditions, if the car is going fast enough, the water can even roll on top of the tyre, eliminating the tyre’s grip. In fact, the very rubber of the tyre itself, which hugs to the road in dry conditions, has been shown to increase the risk of aquaplaning, because it seals tiny pits in the road surface that are full of water, which would otherwise add to the friction.

How to Reduce the Risk

• After water, speed is the biggest factor which contributes to cars aquaplaning. Drive more slowly in wet conditions and give your tyres time to move water out of the way.
• Keep your tyres in good condition. The UK legal limits for tyres are a depth of 1.6 millimetres, but many tyre manufacturers recommend replacing them once the tread is reduced to 3 mm.
• Bald tyres are dangerous whatever the weather.
• Avoid driving through large puddles by keeping a central position in the road, where less water gathers.
• Do not use cruise control in stormy weather.
• Maintain a safe distance from the car in front and aim to drive through their tread marks, to make less work for your tyres.

What to Do if Your Car Aquaplanes

• Look out for a sudden rise in revs and a lightness of steering as your first warning signs.
• Remain calm. If you have cruise control turned on, switch it off using the controls, not by applying a pedal.
• Resist the temptation to steer the car in sudden movements. Allow the car to follow the direction it is moving in, holding the steering wheel steady.
• Reduce the speed by taking your foot off the accelerator slowly, not braking.
• Once you feel the connection with the road again, lightly pump the brake (cars with ABS can brake normally).

Safety is THE number one concern when travelling by car and we hope this information will help you to stay safe in wet conditions.