Braking and stopping distances

By the end of this topic you can

• You can brake progressively to stop smoothly at a chosen point.
• You can keep a safe following gap using the two-second rule.
• You can explain the difference between reaction distance and braking distance.
• You can adjust your speed and gap for wet or icy roads.
• You can brake hard in an emergency while keeping control.

What you need to know and understand

• Total stopping distance is the distance travelled while you react plus the distance the car needs to brake.
• The RSA's minimum stopping distance at 50 km/h is 25 metres dry and 36 metres wet.
• At 80 km/h the minimums are 52 metres dry and 81 metres wet.
• At 100 km/h the minimums are 70 metres dry and 121 metres wet.
• Keep at least a two-second gap in the dry and at least four seconds in the wet.
• The RSA gives these as minimum stopping distances. Real distances are often longer.
• Driving too fast to stop within the distance you can see to be clear is a fixed charge offence: 160 euro and 3 penalty points, or 5 points on conviction in court.

Progressive braking

Plan to stop early. Press the brake gently at first, then firmly as needed, then ease off slightly just before the car stops so it does not jolt. Brake mainly in a straight line, before a bend rather than in it. Check your mirrors before braking so you know what is behind you.

In a manual car, press the clutch down just before the car stops to avoid stalling. In an emergency, brake firmly and quickly and keep both hands on the wheel. Most modern cars have anti-lock brakes (ABS), which let you steer while braking hard. Keep firm pressure on the pedal and do not pump it unless the handbook says to.

The two-second rule

1. Pick a fixed point ahead, such as a lamp post or sign.
2. When the vehicle in front passes it, say 'Only a fool breaks the two-second rule'.
3. If you reach the point before you finish, drop back.
4. In the wet, say it twice. In snow, fog or ice, leave a much bigger gap.

What makes stopping distances longer

Reaction distance in the RSA tables is roughly the speed divided by five, so 10 metres at 50 km/h and 20 metres at 100 km/h, before the brakes even start working.

• Higher speed: braking distance grows far faster than speed.
• Wet, icy or loose road surfaces.
• Worn tyres or brakes, or wrong tyre pressures.
• Tiredness, alcohol, drugs or distraction slowing your reactions.
• Driving downhill or carrying a heavy load.

Common mistakes

• Braking late and hard instead of planning ahead.
• Following too closely, especially in rain.
• Braking while steering hard through a bend.
• Forgetting the clutch just before stopping in a manual car, causing a stall.

Test yourself: Braking and stopping distances

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

Go deeper

• Two Second Rule and Stopping Distances in Ireland