LGV Safe Braking Distances

Question 1

What is the overall stopping distance for a vehicle travelling at 60 mph in ideal conditions (thinking distance plus braking distance)?

Accepted Answer

73 metres (240 feet)

Answer

At 60 mph, the thinking distance is approximately 18 metres and the braking distance approximately 55 metres, giving an overall stopping distance of around 73 metres (240 feet) in ideal conditions. For a loaded LGV, this will be significantly greater.

Question 2

How does vehicle weight affect braking distance for an LGV?

Accepted Answer

Greater weight increases kinetic energy, requiring significantly longer distances to stop

Answer

Kinetic energy increases with mass. A fully loaded LGV has vastly more kinetic energy than a car at the same speed and requires proportionally greater braking distances. This is why LGV drivers must maintain much larger following distances.

Question 3

What effect does a wet road surface have on braking distance?

Accepted Answer

It typically doubles the braking distance compared to a dry road

Answer

A wet road surface approximately doubles stopping distances because the water film between the tyre and road surface reduces friction (grip). LGV drivers must double their following distance in wet conditions.

Question 4

What is 'thinking distance' in the context of stopping distance?

Accepted Answer

The distance the vehicle travels during the driver's reaction time before the brakes are applied

Answer

Thinking distance is the distance covered from the moment a driver perceives a hazard to the moment they begin to apply the brakes. At 60 mph, a driver travels approximately 18 metres during a typical reaction time of 0.67 seconds.

Question 5

What is brake fade and how does it affect LGV braking?

Accepted Answer

Reduced braking efficiency caused by heat build-up in brake components — especially dangerous on long descents

Answer

Brake fade occurs when friction materials and brake drums or discs overheat, reducing their ability to generate friction. For LGVs on long descents, continuous brake application generates extreme heat. Engine braking and gear selection are essential to prevent brake fade.

DVSA UK Driving Theory Practice Test

DVSA UK Driving Theory Practice Test

LGV Safe Braking Distances