DVSA Speed and Stopping Distances 3 — Questions and Answers
Question 1: What effect does a worn tyre tread have on braking distance?
- None — tyre tread is cosmetic
- It significantly increases braking distance, especially in wet conditions, because the tyre cannot disperse water effectively (Correct answer)
- It only affects comfort, not safety
- Worn tyres actually brake better on dry roads
Correct answer: It significantly increases braking distance, especially in wet conditions, because the tyre cannot disperse water effectively
The tyre tread pattern is designed to channel water away from the contact patch. With worn tread, water cannot be dispersed effectively, leading to reduced grip and much longer braking distances, especially in wet conditions. The legal minimum tread depth is 1.6 mm across the central three-quarters of the tyre.
Question 2: What is the minimum legal tyre tread depth in the UK?
- 1.0 mm
- 1.6 mm (Correct answer)
- 2.0 mm
- 3.0 mm
Correct answer: 1.6 mm
The minimum legal tyre tread depth in the UK is 1.6 mm across the central three-quarters of the breadth and around the entire circumference. Driving with tyres below this limit is illegal and carries a fine of up to £2,500 and 3 penalty points per tyre.
Question 3: How do ABS (Anti-lock Braking System) brakes help in an emergency stop?
- They reduce your speed automatically
- They prevent the wheels from locking, allowing you to maintain steering control while braking hard (Correct answer)
- They reduce braking distance in all conditions
- They apply the brakes for you
Correct answer: They prevent the wheels from locking, allowing you to maintain steering control while braking hard
ABS prevents the wheels from locking during heavy braking by rapidly releasing and reapplying the brakes. This allows you to maintain steering control so you can steer around an obstacle while braking. ABS does not necessarily reduce braking distance — on loose surfaces like gravel, it may increase it.
Question 4: How does driving downhill affect your braking distance?
- It has no effect
- It decreases braking distance due to gravity
- It increases braking distance because gravity is pulling the vehicle forward (Correct answer)
- It only affects heavy vehicles
Correct answer: It increases braking distance because gravity is pulling the vehicle forward
Driving downhill increases braking distance because gravity adds to the vehicle's momentum, working against the brakes. The steeper the gradient, the greater the effect. Use a lower gear to help control speed on long descents rather than relying on brakes alone.
Question 5: What factors can increase your thinking distance?
- Weather conditions and road surface
- Tiredness, distractions, alcohol, drugs, illness, and age (Correct answer)
- Only the speed of the vehicle
- The weight of the vehicle
Correct answer: Tiredness, distractions, alcohol, drugs, illness, and age
Thinking distance is affected by anything that impairs your mental alertness and reaction time: tiredness, distractions (mobile phones, passengers, sat nav), alcohol, prescription or recreational drugs, illness, stress, and age. Speed also increases thinking distance proportionally.
Question 6: At 30 mph, what is the approximate thinking distance?
- 6 metres (20 feet)
- 9 metres (30 feet) (Correct answer)
- 12 metres (40 feet)
- 15 metres (50 feet)
Correct answer: 9 metres (30 feet)
At 30 mph, the thinking distance is approximately 9 metres (30 feet). Remember the rule: thinking distance in feet is roughly equal to the speed in mph — so 30 mph gives about 30 feet.
DVSA Speed and Stopping Distances 3
What effect does a worn tyre tread have on braking distance?