Environmental Issues — Car Theory Test Practice

65 original car-theory-test questions on environmental issues, each with the correct answer and an explanation referencing the UK Highway Code. Pass mark 43/50.

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  1. Q1. Which type of vehicle produces the lowest carbon dioxide (CO₂) emissions per km?

    1. A. A large petrol SUV
    2. B. A diesel car
    3. C. A fully electric vehicle (EV) charged on renewable energy Correct answer
    4. D. A hybrid vehicle

    Explanation. A fully electric vehicle charged on renewable energy produces zero tailpipe CO₂ emissions. Charged on the average UK grid it still produces significantly less than any internal combustion vehicle.

  2. Q2. What is the main cause of air pollution from vehicles?

    1. A. Engine heat
    2. B. Exhaust emissions: CO₂, nitrogen oxides (NOx), particulate matter and hydrocarbons from burning fuel Correct answer
    3. C. Tyre wear
    4. D. Engine oil combustion

    Explanation. Vehicle exhaust emissions — particularly CO₂ (climate change), NOx (smog, respiratory disease) and particulate matter — are the main source of transport-related air pollution.

  3. Q3. How can you reduce your vehicle's fuel consumption and CO₂ emissions when driving?

    1. A. Drive at high speed in a high gear to spend less time on the road
    2. B. Drive smoothly: accelerate gently, read the road, maintain steady speed and decelerate smoothly; change up early Correct answer
    3. C. Keep the engine revving to maintain performance
    4. D. Use air conditioning at all times

    Explanation. Smooth, anticipatory driving reduces fuel consumption significantly. Harsh acceleration, high speeds and unnecessary braking all waste fuel and increase emissions.

  4. Q4. Which fuel type currently produces the least harmful particulate emissions?

    1. A. Diesel
    2. B. Petrol
    3. C. Hydrogen fuel cell Correct answer
    4. D. LPG

    Explanation. Hydrogen fuel cells produce only water vapour as exhaust — no particulates and no CO₂ at the point of use. Electric vehicles also produce no tailpipe emissions.

  5. Q5. You leave your engine running while parked waiting for someone. What is the main environmental concern?

    1. A. Overheating the engine
    2. B. Unnecessary idle emissions — fuel is wasted, CO₂ and pollutants are emitted with no benefit, and it is illegal in some areas Correct answer
    3. C. Draining the battery
    4. D. None — idling is harmless

    Explanation. Engine idling wastes fuel and produces unnecessary emissions. It is also an offence under the Road Traffic Act to leave an engine running unnecessarily on a road.

  6. Q6. What is "eco-driving"?

    1. A. Driving only electric vehicles
    2. B. A style of driving that minimises fuel consumption and emissions through smooth, anticipatory driving and good vehicle maintenance Correct answer
    3. C. Only relevant for electric car drivers
    4. D. Driving at very low speeds at all times

    Explanation. Eco-driving techniques include reading the road ahead, smooth acceleration and braking, maintaining steady speeds, changing up early, reducing unnecessary weight, and regular vehicle servicing.

  7. Q7. Which tyre condition most increases fuel consumption?

    1. A. Slightly over-inflated tyres
    2. B. Tyres with excessive tread depth
    3. C. Under-inflated tyres Correct answer
    4. D. New tyres

    Explanation. Under-inflated tyres have increased rolling resistance, which raises fuel consumption and CO₂ emissions. They also wear faster and affect handling. Check pressures weekly.

  8. Q8. What environmental problem is caused by catalytic converters failing on petrol vehicles?

    1. A. Increased CO₂ emissions
    2. B. Increased hydrocarbons, CO and NOx — the catalytic converter converts these to less harmful substances Correct answer
    3. C. Increased fuel consumption only
    4. D. No environmental impact — only affects engine performance

    Explanation. A failing catalytic converter allows unburned hydrocarbons, carbon monoxide (CO) and nitrogen oxides to pass into the atmosphere. These are toxic pollutants and smog precursors.

  9. Q9. How does carrying unnecessary weight in your vehicle affect the environment?

    1. A. No effect
    2. B. It increases fuel consumption and therefore CO₂ emissions Correct answer
    3. C. Only affects very heavy loads
    4. D. Reduces tyre life only

    Explanation. Extra weight means the engine works harder, using more fuel and producing more CO₂. Remove heavy items from the boot when not needed.

  10. Q10. What is the main advantage of using public transport or car-sharing?

    1. A. It is always faster
    2. B. Fewer vehicles on the road means reduced congestion, fuel use and emissions per person transported Correct answer
    3. C. It is free of charge
    4. D. It does not require a driving licence

    Explanation. Car sharing and public transport reduce the number of vehicles on the road, lowering total emissions, reducing congestion and cutting running costs per journey.

  11. Q11. A vehicle emitting excessive black or blue smoke from its exhaust should be:

    1. A. Driven carefully until the next service
    2. B. Repaired before driving again to reduce emissions and potential prosecution Correct answer
    3. C. Only repaired if the MOT is due
    4. D. Allowed to run to burn off excess fuel

    Explanation. Excessive exhaust smoke indicates engine problems (blue = oil burning; black = rich fuel mixture). Both increase harmful emissions and the vehicle may fail an MOT or roadside emissions test.

  12. Q12. How does driving at 80 mph compare to 70 mph in terms of fuel consumption?

    1. A. The same
    2. B. About 10% more fuel at 80 mph
    3. C. About 25% more fuel at 80 mph — aerodynamic drag increases with the square of speed Correct answer
    4. D. Slightly less because the journey takes less time

    Explanation. Aerodynamic drag increases with the square of speed, so driving at 80 mph rather than 70 mph increases fuel consumption by approximately 25% — a significant environmental and financial cost.

  13. Q13. Which vehicle exhaust gas contributes most to global warming?

    1. A. Carbon dioxide (CO2) Correct answer
    2. B. Nitrogen only
    3. C. Oxygen
    4. D. Water vapour

    Explanation. CO2 is a key greenhouse gas.

  14. Q14. Nitrogen oxides (NOx) in exhaust mainly cause:

    1. A. Local air pollution and respiratory problems Correct answer
    2. B. Global warming only
    3. C. Nothing harmful
    4. D. Engine noise

    Explanation. NOx is a key pollutant in urban air.

  15. Q15. Diesel engines emit more of which pollutant?

    1. A. Particulate matter (PM) Correct answer
    2. B. Water vapour
    3. C. Carbon dioxide only
    4. D. Oxygen

    Explanation. Diesels are associated with higher PM output.

  16. Q16. A catalytic converter:

    1. A. Reduces harmful gases in petrol engine exhaust Correct answer
    2. B. Increases engine power
    3. C. Cools oil
    4. D. Charges the battery

    Explanation. Cats convert CO, HC and NOx to less harmful gases.

  17. Q17. Electric vehicles emit:

    1. A. No tailpipe emissions (local) Correct answer
    2. B. High CO2 at tailpipe
    3. C. NOx and PM only
    4. D. More CO than petrol

    Explanation. EVs have no tailpipe emissions.

  18. Q18. Hybrid vehicles typically save fuel by:

    1. A. Capturing energy in braking and using the electric motor at low speed Correct answer
    2. B. Using petrol only
    3. C. Burning hydrogen
    4. D. Solar panels

    Explanation. Regenerative braking and electric assist save fuel.

  19. Q19. Smooth acceleration and braking:

    1. A. Reduces fuel use and emissions Correct answer
    2. B. Increases emissions
    3. C. Has no effect
    4. D. Damages the clutch

    Explanation. Smooth driving is efficient.

  20. Q20. Driving in a higher gear at low revs (where appropriate):

    1. A. Generally reduces fuel consumption Correct answer
    2. B. Increases it
    3. C. Damages the engine always
    4. D. Has no effect

    Explanation. Appropriate higher gears at low revs are efficient.

  21. Q21. Idling the engine while stationary:

    1. A. Wastes fuel and increases pollution Correct answer
    2. B. Warms the engine efficiently
    3. C. Saves fuel
    4. D. Reduces wear

    Explanation. Modern engines warm up best under gentle load; idling wastes fuel.

  22. Q22. Under-inflated tyres:

    1. A. Increase rolling resistance and fuel use Correct answer
    2. B. Save fuel
    3. C. Reduce wear
    4. D. Improve braking

    Explanation. Correct pressures save fuel and tyre life.

  23. Q23. Excess weight in the vehicle:

    1. A. Increases fuel consumption Correct answer
    2. B. Lowers fuel consumption
    3. C. Has no effect
    4. D. Reduces tyre wear

    Explanation. More mass = more energy to move it.

  24. Q24. Aerodynamic drag increases:

    1. A. Exponentially with speed Correct answer
    2. B. Linearly with speed
    3. C. Not at all
    4. D. Only at low speeds

    Explanation. Drag rises roughly with the square of speed.

  25. Q25. Using cruise control on long, flat motorway stretches:

    1. A. Can improve fuel economy by maintaining steady speed Correct answer
    2. B. Always wastes fuel
    3. C. Damages engine
    4. D. Has no effect

    Explanation. Steady speeds help efficiency.

  26. Q26. The London ULEZ is:

    1. A. A zone charging non-compliant vehicles to reduce air pollution Correct answer
    2. B. A car-free area
    3. C. A toll bridge
    4. D. A parking scheme

    Explanation. ULEZ charges high-polluting vehicles.

  27. Q27. Clean Air Zones in UK cities:

    1. A. Target vehicles with higher emissions, sometimes with charges Correct answer
    2. B. Ban all traffic
    3. C. Are for buses only
    4. D. Are decorative

    Explanation. CAZs aim to improve local air.

  28. Q28. Car sharing can:

    1. A. Reduce total emissions per person and congestion Correct answer
    2. B. Increase congestion
    3. C. Raise fuel per passenger
    4. D. Waste energy

    Explanation. Fewer vehicles per person = less pollution.

  29. Q29. Using public transport instead of a car:

    1. A. Generally lowers CO2 per journey Correct answer
    2. B. Uses more fuel
    3. C. Has no environmental impact
    4. D. Always costs more

    Explanation. Buses/trains have lower per-capita emissions.

  30. Q30. A sign of poor engine tune is:

    1. A. Excessive exhaust smoke Correct answer
    2. B. Quiet engine
    3. C. Even tyre wear
    4. D. Full fuel tank

    Explanation. Smoke indicates a combustion problem.

  31. Q31. Blue exhaust smoke suggests:

    1. A. Oil burning in the engine Correct answer
    2. B. Normal operation
    3. C. Diesel fuel
    4. D. Water in fuel

    Explanation. Blue smoke = oil.

  32. Q32. Black smoke from a diesel suggests:

    1. A. Incomplete combustion / rich mixture Correct answer
    2. B. Engine is perfect
    3. C. No issue
    4. D. Clean air

    Explanation. Soot from over-fuelling is common.

  33. Q33. Regular servicing of a vehicle:

    1. A. Helps keep emissions within limits Correct answer
    2. B. Is cosmetic only
    3. C. Increases emissions
    4. D. Voids MOT

    Explanation. Well-maintained engines emit less.

  34. Q34. Driving at 70 mph instead of 50 mph on a steady motorway run typically:

    1. A. Uses noticeably more fuel Correct answer
    2. B. Saves fuel
    3. C. Has no effect
    4. D. Is always safer

    Explanation. Higher speeds increase drag and consumption.

  35. Q35. Anticipating traffic ahead helps the environment because:

    1. A. It reduces unnecessary braking and acceleration Correct answer
    2. B. It uses more fuel
    3. C. It makes no difference
    4. D. It damages tyres

    Explanation. Steady planning cuts fuel use.

  36. Q36. Why should you avoid harsh acceleration?

    1. A. Wastes fuel and increases emissions Correct answer
    2. B. Saves fuel
    3. C. Helps brakes
    4. D. Improves tyre grip

    Explanation. Hard throttle uses more fuel.

  37. Q37. Which is most fuel efficient?

    1. A. Anticipating and maintaining a steady, moderate speed Correct answer
    2. B. Fast acceleration then braking
    3. C. Very slow crawling in low gear
    4. D. Coasting in neutral

    Explanation. Smooth, anticipatory driving wins.

  38. Q38. Hydrogen fuel cell vehicles emit:

    1. A. Water vapour at the tailpipe Correct answer
    2. B. CO2 in high amounts
    3. C. Black smoke
    4. D. NOx only

    Explanation. Fuel cells produce water as exhaust.

  39. Q39. Stop-start systems save fuel by:

    1. A. Shutting off the engine when stationary and restarting when needed Correct answer
    2. B. Running louder
    3. C. Burning more fuel when idling
    4. D. Using the handbrake

    Explanation. No fuel is used while stopped.

  40. Q40. An effective environmental measure is:

    1. A. Combining several errands into one trip Correct answer
    2. B. Making many short trips
    3. C. Warming up for 20 minutes
    4. D. Leaving engine running

    Explanation. Trip chaining reduces cold starts and distance.

  41. Q41. Short journeys with a cold engine:

    1. A. Produce disproportionately high emissions Correct answer
    2. B. Are environmentally efficient
    3. C. Reduce wear
    4. D. Use less fuel

    Explanation. Cold engines burn richer and emit more.

  42. Q42. Modern diesel cars often have a DPF (diesel particulate filter). It:

    1. A. Captures soot and needs regeneration Correct answer
    2. B. Increases soot
    3. C. Is optional
    4. D. Only exists in petrol cars

    Explanation. DPFs trap PM and burn it off periodically.

  43. Q43. AdBlue (DEF) is used to:

    1. A. Reduce NOx emissions in diesel engines via SCR Correct answer
    2. B. Replace diesel
    3. C. Cool the engine
    4. D. Lubricate tyres

    Explanation. SCR with AdBlue cuts NOx.

  44. Q44. Why are ultra-low rolling resistance tyres beneficial?

    1. A. They reduce fuel consumption and CO2 Correct answer
    2. B. They grip poorly
    3. C. They are heavier
    4. D. They increase drag

    Explanation. Low-rolling tyres need less energy.

  45. Q45. What is "eco-driving"?

    1. A. A style of driving that minimises fuel use and emissions Correct answer
    2. B. A racing technique
    3. C. A gear-selection tool
    4. D. A brand of fuel

    Explanation. Eco-driving emphasises smooth, anticipatory driving.

  46. Q46. Which contributes LEAST to reducing emissions?

    1. A. Revving the engine when stationary Correct answer
    2. B. Servicing the car regularly
    3. C. Checking tyre pressures
    4. D. Avoiding idling

    Explanation. Revving stationary wastes fuel.

  47. Q47. Loose fuel cap can:

    1. A. Cause evaporative emissions and warning lights Correct answer
    2. B. Improve economy
    3. C. Clean the tank
    4. D. Help cooling

    Explanation. Evap emissions escape if the cap is loose.

  48. Q48. Driving with open windows at motorway speed:

    1. A. Can increase drag and fuel use Correct answer
    2. B. Reduces drag
    3. C. Has no effect
    4. D. Is always better than A/C

    Explanation. Open windows at speed disrupt aerodynamics.

  49. Q49. Using air conditioning:

    1. A. Adds load on the engine and raises fuel use slightly Correct answer
    2. B. Cools without any cost
    3. C. Improves fuel economy
    4. D. Has no effect

    Explanation. A/C uses engine power.

  50. Q50. Which is best for the environment over a typical long trip at motorway speed?

    1. A. Close windows and use A/C moderately Correct answer
    2. B. Open all windows
    3. C. Drive faster to arrive sooner
    4. D. Use sports mode

    Explanation. Closed windows reduce drag more than A/C costs at high speed.

  51. Q51. Frequent short heavy braking:

    1. A. Wastes kinetic energy and increases emissions Correct answer
    2. B. Saves fuel
    3. C. Is efficient
    4. D. Helps the environment

    Explanation. Braking turns fuel-derived energy into heat.

  52. Q52. Choosing a smaller, more efficient vehicle for your typical use:

    1. A. Lowers emissions and fuel costs Correct answer
    2. B. Is always more expensive
    3. C. Has no impact
    4. D. Worsens emissions

    Explanation. Right-sizing improves efficiency.

  53. Q53. Harsh acceleration and braking:

    1. A. Saves fuel
    2. B. Wastes fuel and increases emissions Correct answer
    3. C. Improves engine life
    4. D. Has no effect

    Explanation. Eco-driving: smooth inputs reduce emissions.

  54. Q54. When stationary for more than a short time you should:

    1. A. Leave engine running
    2. B. Switch engine off to reduce emissions Correct answer
    3. C. Rev the engine
    4. D. Use hazard lights

    Explanation. Highway Code rule 123: Do not leave engine running unnecessarily while stationary on public road.

  55. Q55. Easing off accelerator early and using engine braking:

    1. A. Wastes fuel
    2. B. Reduces fuel use and brake wear Correct answer
    3. C. Damages engine
    4. D. Is illegal

    Explanation. Eco-driving guidance.

  56. Q56. Using air conditioning:

    1. A. Doesn't affect fuel
    2. B. Increases fuel consumption — use moderately Correct answer
    3. C. Decreases fuel use
    4. D. Is illegal

    Explanation. Eco driving: A/C uses fuel.

  57. Q57. Eco-driving tips include:

    1. A. Harsh acceleration
    2. B. Smooth acceleration, anticipation, correct tyre pressures Correct answer
    3. C. Heavy braking
    4. D. High revs

    Explanation. Rule 123: Drive smoothly to save fuel and reduce emissions.

  58. Q58. Idling your engine when parked is:

    1. A. Efficient
    2. B. Wasteful and illegal in some cases Correct answer
    3. C. Required
    4. D. Helpful in cold

    Explanation. Rule 123: Do not leave a vehicle idling unnecessarily.

  59. Q59. Driving smoothly and anticipating hazards:

    1. A. Wastes fuel
    2. B. Saves fuel and reduces wear Correct answer
    3. C. Has no effect
    4. D. Damages engine

    Explanation. Rule 123: Anticipation saves fuel and emissions.

  60. Q60. Correct tyre pressures help by:

    1. A. Reducing fuel economy
    2. B. Improving safety and fuel economy Correct answer
    3. C. Making tyres last less
    4. D. Nothing

    Explanation. Rule 97: Check tyre pressures regularly.

  61. Q61. When stuck in traffic for a long period you should:

    1. A. Rev engine
    2. B. Turn off engine if safe and appropriate Correct answer
    3. C. Sound horn
    4. D. Leave idling

    Explanation. Rule 123: Switch off engine when stationary for a while.

  62. Q62. Reduce environmental impact by:

    1. A. Driving at high speed
    2. B. Servicing the vehicle, driving smoothly, combining trips Correct answer
    3. C. Tailgating
    4. D. Idling

    Explanation. Rule 123: Good maintenance reduces emissions.

  63. Q63. Reducing fuel use also reduces:

    1. A. Emissions Correct answer
    2. B. Tyre wear
    3. C. Engine life
    4. D. Insurance

    Explanation. Rule 123: Fuel-efficient driving reduces emissions.

  64. Q64. Using air conditioning increases:

    1. A. Economy
    2. B. Fuel consumption Correct answer
    3. C. Comfort only
    4. D. Emissions decrease

    Explanation. Rule 123: Air-con uses more fuel.

  65. Q65. At motorway speeds, open windows increase:

    1. A. Economy
    2. B. Drag and fuel use Correct answer
    3. C. Engine cooling
    4. D. Nothing

    Explanation. Rule 123: Open windows increase drag at speed.

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