Environmental issues: HGV theory test questions

Fuel-efficient driving, emissions control, AdBlue and DPFs, idling, noise and reducing your impact. Practise 15 free environmental issues questions with instant answers and explanations – no sign-up.

  • 15 questions
  • Instant feedback
  • Highway Code references

Environmental issues: revision notes

Large vehicles use a lot of fuel, so small changes in driving style make a big difference to cost and emissions.

  • Plan ahead: anticipating hazards means less braking and accelerating, saving fuel.
  • Use the green band on the rev counter and block change gears where appropriate.
  • Switch off when stationary for more than a couple of minutes. Leaving an unattended vehicle running is illegal.
  • Look after the vehicle: correct tyre pressures, regular servicing and a well-set roof deflector all cut fuel use.
  • Emissions systems: AdBlue reduces nitrogen oxides and a diesel particulate filter traps soot. Emissions must not exceed prescribed levels.
  • Noise: don't use your horn while stationary, or in a built-up area between 11.30 pm and 7 am, unless another road user poses a danger.

Check the fuel cap after refuelling; spilt diesel pollutes and makes roads slippery.

All environmental issues questions and answers

Revise every question in this topic. Tap a question to see the correct answer and why.

1Your vehicle is likely to be stationary for more than a couple of minutes. What should you do?
  1. Keep the engine running to keep the air pressure up
  2. Rev the engine to keep it warm
  3. Apply the parking brake and switch off the engine ✓
  4. Leave it idling with the lights on

Answer: Apply the parking brake and switch off the engine. Switching off when stationary for more than a couple of minutes cuts emissions and noise. You can keep it running in stationary traffic or to diagnose faults.

The Highway Code: rule 123

2What's the purpose of AdBlue (diesel exhaust fluid)?
  1. To clean the fuel injectors
  2. To reduce harmful nitrogen oxide emissions ✓
  3. To stop the fuel freezing
  4. To cool the engine

Answer: To reduce harmful nitrogen oxide emissions. AdBlue is injected into the exhaust system to convert harmful nitrogen oxides into nitrogen and water. Keep it topped up.

Vehicle handbook and operator guidance

3What does a diesel particulate filter (DPF) do?
  1. Traps soot particles from the exhaust ✓
  2. Filters the air entering the cab
  3. Cleans the fuel before it reaches the engine
  4. Reduces engine noise

Answer: Traps soot particles from the exhaust. A DPF traps soot from the exhaust. It needs to regenerate regularly, so follow the warning lights and handbook advice.

Vehicle handbook and operator guidance

4What does 'block changing' gears mean?
  1. Changing up through every gear in order
  2. Holding the clutch down between gears
  3. Changing gear without the clutch
  4. Missing out intermediate gears when it's appropriate ✓

Answer: Missing out intermediate gears when it's appropriate. Block changing means skipping gears that aren't needed. It saves fuel and reduces wear.

Vehicle handbook and operator guidance

5Where on the rev counter should you usually keep the needle for the best fuel economy?
  1. In the red band
  2. As low as possible, even if the engine labours
  3. In the green band ✓
  4. As high as possible before changing up

Answer: In the green band. The green band shows where the engine works most efficiently. Changing gear within it saves fuel.

Vehicle handbook and operator guidance

6How does planning well ahead help the environment?
  1. It lets you drive in a lower gear
  2. You brake and accelerate less, so you use less fuel ✓
  3. It allows you to keep the engine at high revs
  4. It means you can ignore speed limits

Answer: You brake and accelerate less, so you use less fuel. Planning ahead lets you keep moving smoothly, reducing harsh braking and acceleration. That cuts fuel use and emissions.

The Highway Code: rule 146

7How do under-inflated tyres affect your vehicle?
  1. They increase fuel use and affect braking and steering ✓
  2. They reduce fuel use
  3. They make the ride smoother and safer
  4. They have no effect on a large vehicle

Answer: They increase fuel use and affect braking and steering. Under-inflated tyres increase rolling resistance and fuel use. Your brakes and steering will also be affected.

The Highway Code: Annex 6

8You're stationary on the road in a built-up area at 11.45 pm. When may you use your horn?
  1. To let a customer know you've arrived
  2. To greet another driver
  3. Whenever you need to
  4. Only if another road user poses a danger ✓

Answer: Only if another road user poses a danger. You must not use your horn while stationary, or in a built-up area between 11.30 pm and 7.00 am, except when another road user poses a danger.

The Highway Code: rule 112

9Why should you check that the fuel cap is secure after refuelling?
  1. So the engine starts more easily
  2. So the fuel gauge reads correctly
  3. Spilt diesel pollutes and makes the road very slippery ✓
  4. So the tachograph records the refuel

Answer: Spilt diesel pollutes and makes the road very slippery. Diesel spills are dangerous, especially to motorcyclists, and harm the environment. Make sure the cap and seal are secure and don't overfill.

The Highway Code: Annex 6

10Which TWO help to reduce harmful emissions from your vehicle? Mark two answers.
  1. Revving the engine before switching off
  2. Keeping the vehicle well serviced ✓
  3. Driving in a lower gear than necessary
  4. Planning your route to avoid congestion ✓

Answer: Keeping the vehicle well serviced; Planning your route to avoid congestion. A well-maintained engine and avoiding congestion both reduce emissions. Revving and using low gears unnecessarily waste fuel.

The Highway Code: Annex 6

11What does the law say about your vehicle's exhaust emissions?
  1. They must not exceed the prescribed levels ✓
  2. They only matter on motorways
  3. They're only checked when the vehicle is new
  4. They don't apply to diesel engines

Answer: They must not exceed the prescribed levels. Exhaust emissions must not exceed prescribed levels. Faults that cause excess smoke should be fixed quickly.

The Highway Code: Annex 6

12Why should a lorry's cab roof air deflector be adjusted to suit the trailer height?
  1. To make the cab quieter for the driver
  2. To reduce the vehicle's travelling height
  3. To keep rain off the trailer
  4. To reduce wind resistance and save fuel ✓

Answer: To reduce wind resistance and save fuel. A correctly set deflector smooths the airflow over the trailer, which reduces drag and fuel use.

Vehicle handbook and operator guidance

13How can operators reduce the number of empty lorries on the road?
  1. By using bigger engines
  2. By driving faster on the return journey
  3. By planning return loads (backloads) ✓
  4. By removing the trailers

Answer: By planning return loads (backloads). Planning return loads means fewer empty miles, which saves fuel and cuts congestion and emissions.

Vehicle handbook and operator guidance

14Where should you wash out a road tanker?
  1. In any roadside drain
  2. Only at an approved cleaning facility ✓
  3. In a lay-by using a hose
  4. Into a nearby stream

Answer: Only at an approved cleaning facility. Residues can be harmful to the environment. Use approved facilities so waste is dealt with properly.

GOV.UK: Moving dangerous goods

15You're delivering at night in a residential area. What should you do?
  1. Keep noise to a minimum, such as switching off the engine and closing doors quietly ✓
  2. Sound your horn to let the customer know you've arrived
  3. Keep the engine running so the refrigeration unit is loud enough to hear
  4. Unload as quickly as possible, however much noise it makes

Answer: Keep noise to a minimum, such as switching off the engine and closing doors quietly. Night-time noise disturbs residents. Switch off when you can and handle cages and doors quietly.

The Highway Code: rule 112

Frequently asked questions

What does AdBlue do?

It's injected into the exhaust to turn harmful nitrogen oxides into nitrogen and water.

Should I leave the engine running while waiting?

No. If you'll be stationary for more than a couple of minutes, apply the parking brake and switch off.

What is block changing?

Skipping intermediate gears when they're not needed, which saves fuel and reduces wear.

Original practice questions based on The Highway Code (Open Government Licence v3.0). Not the real test questions. MockTheory is not affiliated with or endorsed by the DVSA.

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