Driving tips for flooded roads

Driving in hazardous conditions

20 March 2018

Driving on flooded roads can be dangerous. If you can't postpone your trip, here are some pointers for staying safe and avoiding damage to your car's engine.

With heavy rain a year-round fixture in the UK, floods are unfortunately a fairly frequent occurrence.

Although large-scale, destructive flooding often gets high billing on the news, unreported localised flooding is actually surprisingly commonplace – so it’s important to know how to approach a flooded road, not only to look after your own safety, but also to avoid damaging your car's engine or exhaust.

Trunk roads

Although water is obviously a liquid, it can sometimes behave more like a solid under certain conditions. When a car tyre hits standing water at speed, the water may effectively form a 'cushion' that makes the tyre lose traction, preventing it from touching the tarmac below. This dangerous process, which can rob you of control of your car, is known as aquaplaning.

On flooded dual-carriageways or motorways, it's therefore best to stay below 50mph at all times to reduce the risk of aquaplaning. Large roads like these are often closed during floods, so it's advisable to either postpone any non-essential travel or check the latest traffic information before setting off, in case you need to plan an alternative route.

If you are driving on a flooded road, be especially careful along downhill stretches – ease off the accelerator and cover the brake until you're on level ground to minimise the danger.

Rural roads

Country roads are often worst affected by floods, as the lack of drainage on rural routes means water has nowhere to go, other than pooling on the tarmac. This can pose a serious problem for drivers, as particularly deep expanses of water (just six inches is enough to reach the bottom of most cars) can cause water to enter the exhaust – causing damage to the engine and potentially sparking a breakdown.

It’s sometimes possible to gauge the depth of flooding using surrounding objects as reference points, but if you're in doubt about the depth of a puddle, or suspect it may be more than six inches deep, it's best to avoid it.

Be particularly wary of moving flood waters, as there have been cases of fast-moving currents carrying cars off into deeper water, which can put passengers in danger. If running water is more than four inches deep, steer clear.

Urban roads

Our towns and cities usually have roadside drainage that prevents flood water from gathering, but drains can become overwhelmed in particularly heavy rain. If a road is obviously flooded, try to switch to an alternative route along side streets, while avoiding the danger of last-second manoeuvres.

If you have to travel through any shallow puddles, be mindful of nearby pedestrians and approach slowly, from towards the middle of the road – surprisingly, splashing pedestrians is an offence under Section 3 of the Road Traffic Act 1988.