With the recent flooding that’s happening in Shrewsbury, its a timely reminder on how we as drivers are expected to deal with flood water how to drive through it safely.
The Dangers of driving through floodwater
Urban flood water can carry dangerous bacteria from drains and sewers that could cause disease.
Rural flood water is more likely to be contaminated by agricultural chemicals and animal waste.
Cold water reduces your muscle strength – 20 minutes in water at 12C lowers muscle temperature from 37ºC to 27ºC, reducing strength by 30%.
Just 15cm of fast-flowing water can knock you off your feet and be enough for you not to be able to regain your footing.
It’s a challenge to stand in waist-deep water flowing at only 1m/s. By 1.8m/s (4mph) everyone is washed off their feet.
If the speed of the flood water doubles, the force it exerts on you or your car goes up four times.
Just 60cm of standing water will float your car.
Just 30cm of flowing water could be enough to move your car.
A mere egg cupful of water could be enough to wreck an engine.
Flood water can be contaminated and carry diseases.
Driving dangers to watch for in floodwater
What to watch out for
Look out for slip and trip hazards like kerbs under the water.
Manhole covers can get lifted and moved.
Water levels can change quickly.
Assume that flood water is contaminated:
Large potholes hidden under the water, could mean that you could suddenly drop lower in the water, or at worst cause a flat tyre that cannot be repaired whilst in the water, leaving you stranded and unable to move.
Heavy rain showers combined with fallen leaves can create flash floods – and they can spell trouble for drivers. Find out how to drive through patches of localised flooding in our advice guide…
When you have to pass through a flood, take your time. Stop and assess how deep the water is. Don’t just drive into it. Some roads that are likely to flood have depth gauges. Check the depth on these.
If the water seems too deep for your vehicle, turn back and go around the flood by another road. It might take a little longer, but that’s better than finding yourself stranded.
If the water is too deep it could:
· flood the exhaust, causing the engine to stop
· find its ways into the air intake on some vehicles, causing serious engine damage
If the water isn’t too deep, drive on slowly but be sure to keep to the shallowest part. Remember, because of the camber of the road, the water is probably deepest near the kerb and shallowest at the crown.
Driving through floodwater
Drive in first gear as slowly as possible but keep the engine speed high and steady by slipping the clutch.
If the engine speed is too low, you might stall.
If you go too fast, you could create a bow wave. Water will flood the engine and it could cut out.
Try to strike a balance.
Test your brakes
Water can reduce the effectiveness of your brakes, so test your brakes whenever you’ve passed through water on the road. When you’ve driven safely through, check the mirrors first, and then test your brakes.
If they don’t work properly, it will help to dry them out if you apply light pressure to the brake pedal while driving along slowly. Don’t drive at normal speed until you’re sure they’re working properly.
Take an alternative route
It sounds obvious but the amount of times people who have been trapped in vehicles in flood water, have said I didn’t want to go the longer way around – would scare you!
Flood water how to drive through it safely
Never drive through deep, fast-flowing water and don’t drive through flooded roads if you can avoid them. It’s better to add an extra 10-15 minutes to your journey rather than risk your car’s engine and electrics being ruined, or even worse the vehicle being swept away.
3. Let oncoming vehicles pass
Wait for oncoming vehicles to get through the flood patch before you head into it, especially if they’re large vehicles or are traveling fast because they could soak your vehicle and cause it to break down.
4. Drive along the highest point of the road
Most roads dip down at either side, so aim to drive in the middle of the road. That’s another reason to wait for oncoming cars to get out of the way before attempting to cross floodwater.
5. Don’t drive too fast
Drive through flood water slowly – 3-4mph is an adequate speed. If you drive too fast you not only will you create a wave that’ll splash other road users, you’ll also run the risk of your car’s tyres losing their contact with the road. If this happens, don’t brake, just take your foot off the accelerator and keep the steering wheel straight and wait for the grip to return.
6. Don’t stop
Although you should drive slowly, it’s important not to let the car come to a halt while crossing deep water because that could allow water to get into the exhaust pipe, which can cause costly damage. Keep the engine revs up, too; if necessary slip the clutch to do this in a car with a manual gearbox. If you’re driving an automatic, select the lowest possible held gear and keep your foot on the accelerator.