Six helpful tips for driving in heavy rain

Tuesday, 31 January 2023

Rain is forecast for many parts of the North Island.

With rough weather forecast for Northland and Auckland, and other parts of the North Island, despite it legally being summer now, we thought it a good time to go over some tips for driving in the rain.

Of course, if you don’t have to drive, the best thing to do is just stay home.

Headlights

First off, headlights. A good rule of thumb is: if you need your windscreen wipers, you need your headlights.

Driving through flooded roads takes a bit of knowledge and care.

* Here's how to stay safe on the roads in bad weather

* Six tips to stay safe on the roads during a weather bomb

* Wet weather driving tips for the school holiday

Drive to the conditions. Standing water on a road surface can quickly lead to aquaplaning.

Automatic light settings will not always activate in bad weather conditions, so it is up to you to make a sensible decision as to whether these need to be turned on.

If your car is fitted with daytime running lights (DRLs), you still need to switch your main lights on. DRLs are designed to make your vehicle more visible to other road users during the day. Just like you wouldn’t rely on your DRLs for your night vision, or to make your car visible at night, you shouldn’t just rely on them in bad weather either.

Space out when following someone in the rain. No, not that sort of space out – extend your following distance.

Flooded roads

Tackling flooded roads requires a degree of knowledge and finesse. If you are familiar with the road, you can judge the flood depth in relation to the kerb, but remember the road surface beneath the water might have broken up into potholes or dips, making the road much less safe.

If you come across a flooded road and it’s standing water (don’t even try crossing if the water is moving), slow down. Right down. Drive as if you are doing a hill start, keeping the engine revs ticking over. This will prevent water from entering your exhaust. If you are in an automatic car, accelerate slightly but control the speed with your brakes.

Your tyres are the most important part of your car. Keep them up to scratch.

If a car is coming towards you before you’ve entered the flooded area, switch your engine off and wait for their bow wave to pass. Water can easily come over a car’s bonnet and into the intakes, which can quickly ruin an engine.

Aquaplaning

If water is standing in puddles on the road surface, your car is at risk of aquaplaning, or hydroplaning.

Electric vehicles have good waterproofing around their critical components, but you should still try and avoid driving them.

Aquaplaning is where a wedge of water forms in front of the tyre and lifts it up off the road surface. This is caused by the tread not being able to displace the amount of water present.

To recover from aquaplaning, ease gently off your accelerator, have a firm grip of the steering wheel and be sure not to make any sudden steering actions. The car will eventually regain its grip as the water clears.

Following distance

We all know the two-second rule: count 'one thousand and one, one thousand and two' as the car in front passes a static object and if you pass it before you've finished counting, you're too close.

But in difficult driving conditions, you should actually apply the four-second rule to account for reduced visibility and increased stopping distances.

If you want to really be safe, get even further behind. You still want to be able to see the car in front – driving rain can really impact visibility so keep those taillights in vision – but don’t force yourself hold to a four-second gap if you’d rather be five or six.

Keep your car up to scratch

Finally, keep up the maintenance of your car. This is obviously easier in a garage but, considering not everyone has that luxury, they need to be done ahead of time.

This means checking your windscreen for cracks, making sure your wiper blades work correctly and your front and rear demisters functions as well. You should also have a look at your battery for corrosion, checking the electrolyte levels too, and replacing as needed.

Tyres are hugely important too, they’re your only contact point with the road so make sure they’re fresh, without cracks and have plenty of tread.

What about electric vehicles?

While it’s a good idea not to mix electricity and water if you can avoid it, electric vehicles are waterproofed to an extent.

Batteries come with an Ingress Protection (IP) rating, which refers to the level of protection of an electrical enclosure against dust and liquids. Most are rated at IP67, which means the battery will keep working even if it’s submerged under up to one metre of water for up to half an hour.

Safety equipment like the ground-fault detection system constantly tests for electric connections between the vehicle chassis and the high voltage system, as the two must be isolated from each other. If they do come in contact, the ground-fault system will shut off the electrical supply to prevent damage.

Should that waterproofing fail, there is a risk of the battery shorting and starting a fire. There’s not much you can do at this point, aside from getting well away from the car. A burning or heated battery releases vapours like sulphuric acid, oxides of carbon, nickel, lithium, copper, and cobalt, all of which are toxic to humans.