CPC Vehicle Safety Checks 2 — Questions and Answers
Question 1: What is the minimum brake efficiency required for HGV service brakes at annual test?
- 30%
- 50% (Correct answer)
- 45%
- 35%
Correct answer: 50%
UK annual test standards require service brakes on HGVs to achieve a minimum efficiency of 50%, ensuring adequate stopping power for the vehicle type and weight.
Question 2: Under-inflated tyres on an HGV are dangerous because they:
- Improve grip in wet conditions
- Overheat, leading to structural failure and potential blowout, and increase fuel consumption and tyre wear (Correct answer)
- Reduce rolling resistance for fuel economy
- Cause the load to shift towards the under-inflated axle
Correct answer: Overheat, leading to structural failure and potential blowout, and increase fuel consumption and tyre wear
Under-inflation causes the tyre sidewall to flex excessively, generating dangerous heat that can cause structural failure and blowout, increases fuel consumption and accelerates irregular tyre wear.
Question 3: What type of fire extinguisher should be carried in the cab of an HGV, and what class of fire is it for?
- CO₂ for electrical fires only
- Dry powder or CO₂ suitable for Class A (solids), B (liquids) and electrical fires (Correct answer)
- Wet chemical for cooking fires
- Water for wood and paper only
Correct answer: Dry powder or CO₂ suitable for Class A (solids), B (liquids) and electrical fires
HGV cabs should carry a powder or CO₂ extinguisher suitable for the types of fire likely in a cab (fuel, electrical and general materials), covering multiple fire classes.
Question 4: Air brake systems must have sufficient pressure before moving the vehicle. What happens if air pressure is too low?
- The engine cuts out automatically
- A warning alarm sounds and the spring brakes automatically apply preventing movement (Correct answer)
- The steering locks
- The transmission disengages
Correct answer: A warning alarm sounds and the spring brakes automatically apply preventing movement
Air brake systems are fail-safe: low air pressure triggers a warning and the spring (park) brakes apply automatically, immobilising the vehicle until sufficient pressure is built up.
Question 5: What is the purpose of checking the coupling mechanism of a semi-trailer before driving a combination?
- To comply with speed limiter requirements
- To ensure the fifth wheel coupling is fully engaged and locked, preventing separation of the tractor and trailer unit during movement (Correct answer)
- To check the trailer's tachograph is recording
- To verify the trailer's MOT certificate
Correct answer: To ensure the fifth wheel coupling is fully engaged and locked, preventing separation of the tractor and trailer unit during movement
An insecure fifth wheel coupling can result in trailer separation at speed — a catastrophic and potentially fatal event; visual and physical coupling checks are essential before every departure.
Question 6: How often must a digital tachograph vehicle unit be calibrated?
- Every year
- Every 2 years or after any relevant repair or modification (Correct answer)
- Every 6 months
- Only when the vehicle changes operators
Correct answer: Every 2 years or after any relevant repair or modification
Digital tachograph vehicle units must be calibrated by an approved centre every 2 years, or following any repair or modification that might affect accuracy.
CPC Vehicle Safety Checks 2
What is the minimum brake efficiency required for HGV service brakes at annual test?