Driving tests

What should you do if your brakes fail while you are driving?

Depending on what vehicle you are driving and the type of road you are driving on, you have a number of options if your brakes stop working while you’re driving.

They could stop working because of brake fade, you’ve driven through water, or a mechanical issue. If you lose your brake fluid, the brake warning light will appear on your dashboard.

Sudden brake failure is extremely unlikely. Even if your power-assisted brakes fail, you can still usually apply braking power by pressing harder on the brake pedal.

In some countries there are emergency escape lanes on long downhill stretches that vehicles that experience brake failure can use, but they are not everywhere. Let’s talk about predominantly flat roads first, though.

Get out of the way of other traffic

Other traffic needs to know what you are doing, so your indication is important. If you need to move to the left off the road or across lanes, signal left and try to move into a gap.

On a motorway with a hard shoulder, try to get to the hard shoulder as there is less likely to be anything in it for you to hit as you slow down.

Pump the brakes

If the pedal goes to the floor, pump it a few times then push it to the floor. There might not be much braking, but anything is better than nothing.

If the pedal feels rigid, is there anything lodged underneath it, like your floor mat?

Give clear signals

Putting your hazard warning lights on will let other drivers know you are experiencing difficulties.  Use your horn.

Use your gears

Lower gears provide more engine and mechanical resistance – this is called engine braking. Be careful not to over-rev the engine, though. You may need to step down through your gears as you lose speed. In a car with a manual gearbox, this is straightfoward. In a car with an automatic gearbox you might have an L setting, or you could have sequential-style gears where you can change down with paddles behind the steering wheel, or a gear lever. Simply keep changing down a gear every time the revs drop to a couple of thousand below the red line.

Engine braking will reduce your speed to 5-10km/h but no more – your car will continue to creep forward.

Don’t put your car into reverse while you are going forwards because you risk causing a huge amount of damage to your gearbox.

Turn on the air conditioning and accessories

The air conditioner should be turned onto the coldest setting with the highest fan speed. This will absorb a couple of kilowatts of power. Turning on all accessories, such as the heated rear window and your lights, will also create some drag on the alternator.

Use the handbrake

Don’t pull the handbrake on at high speed because you risk spinning out. There’s also the risk that it could overheat and become ineffective. Wait until engine braking has dropped your speed to below around 20km/h, then pull the handbrake on gradually. The handbrake only works on the rear wheels and if they skid you could lose control, so be careful.

Can you apply an electric handbrake when driving at speed?

If you have a newer hydraulic handbrake/electric parking brake most modern cars will perform a controlled deceleration if you hold the switch on.

Brake failure while towing

Some trailers have separate trailer brakes which might be able to be applied. If the trailer is fairly light, it won’t slow you down quickly, but it will help.

Engine braking

Trucks often have compression release engine braking which uses pressure in the engine to slow a vehicle down.

Use the road contours

If you see a side road that is uphill, you can turn up it to stop more quickly.

Use kerbs and the edge of the road

Gently running your wheels against the kerb won’t do wonders for your tyres or alloy wheels, but it will create extra friction. The same applies for concrete dividing barriers on motorways.

Grass verges will create more resistance, but they will increase your risk of spinning out.

Hedges and bushes will damage your paintwork, but have been used before in an emergency.

Rough stone walls are not so good as the corner of the vehicle will catch on the wall and it will spin it around (or flip it over) like this.

Electric vehicles

Electric vehicles have regenerative braking and this provides a level of resistance which is used to charge the battery. Many electric vehicles have a ‘B’ mode (sometimes even B1, B2, B3, B4, etc) to indicate how much regenerative braking will be used. Use this mode if your brakes fail; in some electric cars, the highest setting is as good as applying your brakes moderately.

Steep slopes

Long mountain roads can make your brakes fade.

If you’re on a very steep slope, engine braking might only slow the rate of acceleration, i.e. you’ll still pick up speed, just less slowly. If you change gear, your car will pick up speed while the gearbox is between gears.

It’s critical you act quickly in this situation. You need to make a decision:

Can I ride out this bit of the hill then deal with actually stopping when the gradient levels out, or do I need to stop now?

The only reason you’d choose the first one is if you know the road, the rate of acceleration isn’t high, there’s not much traffic around and you’re confident in your vehicle’s ability.

If it’s the second one, you have a number options to help you:

  • Verges, hedges and bushes will slow you down; trees will stop the car dead unless they are saplings
  • Escape roads are the best option
  • You can (gently) run into the back of a bigger vehicle which will then brake and slow you down. But, be careful you won’t create a much bigger accident

Things not to do if your brakes fail

  • Don’t put your gearbox into neutral or you’ll have no engine braking.
  • Don’t put your gearbox into reverse unless you want it to be converted to thousands of tiny metal shards (and you’ll have no engine braking).
  • Don’t weave from side-to-side at high speed. Yes, it creates more friction, but you risk spinning out, and if your brakes have failed, any electronic stability control measures (which work by braking individual wheels) might not work. At low speed, it’s probably fine.
  • Don’t stop the engine – you’ll lose your power steering

When you’ve stopped

Hopefully you’ve managed to pull off the road and out of the way of other traffic. Put your hazard warning lights on. If you’ve just overheated your brakes, you can wait for them to cool, then limp home at a slow speed. You will need to change your brake fluid and gets the brake rotors and pads checked (you may have glazed the pads which will make them much less effective).

If there’s something wrong with the brakes, get your car towed.

In brief: what to do if your brakes fail

  1. Get out of the way of other traffic
  2. Pump your brakes
  3. Give clear signals
  4. Use your gears
  5. Use your handbrake or electronic parking brake
  6. Turn on your air conditioning
  7. Look for uphill escape routes
  8. Use kerbs, verges and bushes
driver training

Darren is a member of the Institute of Advanced Motorists and the NZ Motoring Writers' Guild

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