Aquaplaning

 

Aquaplaning, also known as hydroplaning, is a phenomenon which occurs when a car's tyres are no longer able to clear surface water from its path.  This leads to a layer of water building up in front and under the affected tyres effectively "lifting" them and reducing their contact with the road.  As soon as this happens, steering becomes unresponsive and the car will most likely skid or slide out of control.  This is not to be confused with skidding on a wet surface where standing water is not present.

Road tyres are designed to optimise clearing water from its path through the design of the tread grooves.  To maximise on this feature, the tyre needs sufficient time to clear that water hence why aquaplaning is speed related.  When driving through standing water the tyres have to work harder to disperse the excessive water from its path, the faster the wheels rotate the less time the tyre has to disperse that excessive water.  Whilst aquaplaning can happen at speeds as low as 30mph, it is at its most critical at speeds of around 54mph + according to NASA research.  Standing water can be as little as just 1/10 inch deep to be sufficient to cause aquaplaning.

 

aquaplaning 1

 

How to prevent aquaplaning

Two main factors contribute to aquaplaning - Water and Speed.  Ok so we can't remove the water but we can control our speed. 

When driving in the rain where standing water is likely on the road, the normal driving advice is to reduce your speed to a suitable pace which is safe for the conditions and hazards.  Your stopping distance is doubled on wet roads and more so if aquaplaning actually occurs.  By reducing your speed, you will have more time to "see and assess" standing water on the road ahead, react early and, as explained above, allow the tyres more time to disperse the water therefore retaining their grip on the road surface.  Also be aware of puddles near the kerb where pedestrians are nearby. 

So what can we do to recover from aquaplaning

The clues to aquaplaning occurring whilst driving are;

  • Steering suddenly becoming light and unresponsive
  • Possibly a rise in the engine revs if the driven wheels start to spin
  • The feel of "gliding" along
  • Stability loss

As soon as aquaplaning occurs, immediately reduce your speed by backing off the gas (accelerator) DO NOT BRAKE at this point.  Keep a firm grip on the steering wheel with both hands maintaining either a straight line or slowly easing it towards the intended direction of travel (aquaplaning can also happen on bends).  DO NOT APPLY HARSH STEERING.  As soon as the speed reduces, the weight of the car will help push the tyres back down through the water and regain grip on the road.

Common Risk Areas

Typical higher risk areas where aquaplaning after a rainfall is likely are;

  • Low lying areas such as under a bridge where water can't drain away quickly.
  • On roads where a camber causes water to collect on one side, especially on left hand bends.
  • Along dual carriageways and motorways where the left-hand lane is regularly used by lorries.  The weight of the lorries can cause "ruts" or "tramlines" to form.  These ruts or tramlines can trap water.   Ruts can also form on busy A roads.
  • Near rivers, at the base of a hill or in any dip in the road after a heavy rainfall.
  • Very near where a water main has burst or a drain has overflowed.

The list here could go on and on but basically aquaplaning can occur anywhere where water is unable to drain away quickly.

Using "cruise control" in the rain

Contrary to belief, cruise control will not suddenly cause your car to increase speed and "fly through the air" when aquaplaning.  If cruise control is active, then the driven wheels will not exceed the pre-set speed control setting.  However, by using cruise control, should aquaplaning occur your reaction time to reduce the speed may be much slower therefore prolonging the problem.  There is also the danger of "panic" braking.  For this reason only it is strongly advised that you DO NOT USE cruise control in the rain.

 

aquaplaning 2