Braking and stopping distances

By the end of this topic you can

• You can explain reaction distance, braking distance and total stopping distance.
• You can describe how speed, wet roads and slopes change stopping distance.
• You can keep a safe following gap using a time count.
• You can brake smoothly in normal driving and firmly in an emergency.

What you need to know and understand

• Total stopping distance = reaction distance + braking distance.
• An alert driver takes around three-quarters of a second to react. At 60 km/h the car travels about 12 metres in that time.
• Double your speed and your reaction distance doubles.
• Double your speed and your braking distance roughly quadruples. If a car needs 20 metres to brake from 50 km/h, it needs about 80 metres from 100 km/h on the same surface.
• Braking distance increases on wet, slippery, uneven or unsealed roads and when going downhill.
• Recommended following gaps vary by state: Victoria and WA suggest at least 2 seconds, while NSW, SA, Tasmania and the NT suggest 3 seconds. Leave more in poor conditions.

Why a little extra speed matters a lot

Because braking distance grows with the square of speed, small increases have a big effect. At a higher speed you also cover more ground before your foot even reaches the brake. That is why driving just a few km/h over the limit in a busy street can turn a near miss into a crash.

Braking smoothly

Brake in a straight line before a bend, not while turning. A car is more stable and easier to control when braking happens before the corner.

1. Check your mirrors so you know what is behind you.
2. Ease off the accelerator early.
3. Apply light pressure to set up the brakes.
4. Squeeze progressively harder as needed.
5. Ease the pressure slightly just before stopping for a smooth finish.

Emergency stops and ABS

Most modern cars have anti-lock brakes (ABS). In an emergency, press the brake hard and keep pressing. The pedal may pulse or shudder; that is ABS working, so do not ease off. ABS helps you keep steering control, but it does not make the car stop in a much shorter distance on a slippery road.

Measuring your following gap

Pick a fixed object such as a pole. When the car ahead passes it, count the seconds until your car reaches it. If you get there before the count for your state, drop back. Double the gap or more in rain, at night or behind trucks and motorbikes.

Common mistakes

• Following too closely in traffic. Rear-end crashes are among the most common crashes.
• Braking hard in the middle of a bend.
• Easing off the pedal when ABS pulses in an emergency.
• Using the same gap in the wet as in the dry.

Test yourself: Braking and stopping distances

Answer each question, then read the explanation. Questions come in a random order each time.