How to drive through flooded roads

Carlton Boyce / 08 September 2015 ( 22 November 2016 )

Floods can strike at any time and while a flooded road might not look especially dangerous the reality is that few driving conditions are as hazardous.



A depth of just 6 inches (15cms) is deep enough to float some cars and two feet (60cms) will float just about any car, even heavy four-wheel-drives, especially if the water is moving, as will be the case in a ford or flash flood – and once your car is floating you are no longer a driver and are simply there as ballast…

Stay safe driving in wet weather

Here are out top tips for dealing with flooded roads.

  • The first tip is the most important: only drive through a flood if there is absolutely no other way round it. Even a 20-mile detour is worthwhile if it means you don’t have to negotiate a flooded road.

  • If you have no choice but to drive through a flood, you should get out and walk through it first. (This is where an emergency stash of wellington boots and a walking stick will pay dividends!) Use the stick to help keep your balance and to prod the water in front of you; better it finds the deep pothole than you stumble over…

  • If the flood is deeper than the top of your wellies, it’s too deep to drive through.

  • If the water is moving, then four inches (10cms) is the maximum depth you should consider driving through.

Six obscure motoring laws you probably don't know

  • If the flood has been caused by a flash flood, be extra vigilant as the road itself may have been washed away, leaving an uneven, muddy mess where there was once solid tarmac.

  • Aim to drive through a flood by using the centre of the road. This is where the tarmac is highest and the water lowest. If necessary, wait until the way ahead is clear of other traffic to allow you to do so. If you can’t see the whole stretch clearly, you probably shouldn’t drive it at all.

  • Once you are moving through the water, you need to maintain a speed roughly equivalent to a brisk walking pace. This will build up a small bow wave that will create a depression behind it, effectively reducing the depth of water your engine bay is moving through. This significantly reduces your chances of drowning the engine and electrical system.

Tips for tackling motorway driving

  • If necessary, ‘slip’ the clutch to keep your engine revs high and your speed slow. It’s important not to stall your engine as the exhaust gases are the only thing stopping water getting into your exhaust pipe.

  • For the same reason, it is important not to change gear while you are driving through a flood. Stay in first or second gear until you are out of the water.

  • In an automatic car, where there is no clutch to ‘slip’, try braking gently with your left foot while using your right foot on the accelerator. It takes practice but is a good way to keep engine revs up and your speed down.

  • Be aware of other vehicles and pedestrians; you don’t want to swamp them with water as you pass.

  • Even a couple of centimeters of water can be lethal as it can cause your car to aquaplane, especially on fast roads like motorways and dual carriageways. Aquaplaning is when your tyres are no longer touching the tarmac and are gliding on a cushion of water, causing you to lose all steering control and the ability to brake. To regain control you’ll need to gently ease off the accelerator until your speed reduces, allowing your tyres to regain grip. Avoiding the problem altogether is a matter of having correctly inflated tyres with a decent amount of tread on them and keeping your speed down in wet conditions.

  • Once you are safely out of the water dry your brakes. This is done by simply applying them gently at slow speed when it is safe to do so.

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