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Difficulty: MediumEnvironmental Impact and Fuel Efficiency

Driving at a sustained speed of 70 mph can increase a vehicle's fuel consumption by up to 30% compared to driving at 50 mph.

Answer: Answer

Answer

True. Driving at 70 mph uses up to 30% more fuel than driving at 50 mph due to the sharp increase in aerodynamic drag.
The statement is true because air resistance rises rapidly as vehicle speed increases. Overcoming this higher aerodynamic drag requires greater engine power output, causing fuel consumption to increase by up to 30% at 70 mph compared to 50 mph.

Step-by-Step Solution

1
Examine the physical relationship between vehicle road speed and aerodynamic drag.
Aerodynamic resistance increases exponentially as vehicle speed rises, meaning the power required to push the car through the air at 70 mph is considerably higher than at 50 mph.
Air resistance is the primary resistive force acting on a vehicle at motorway speeds.
2
Evaluate the fuel consumption differential established by DVSA eco-safe driving benchmarks.
The extra engine load needed to overcome increased air resistance results in up to a 30% increase in fuel consumption when cruising at 70 mph compared to 50 mph.
Fuel injection rates must increase to maintain engine power output against higher aerodynamic forces.
3
Determine the accuracy of the statement.
The statement matches official DVSA figures and environmental guidelines exactly.
Maintaining moderate, legal cruising speeds directly reduces fuel burn and carbon emissions.

Key Concept

Vehicle Speed, Aerodynamic Resistance, and Fuel Consumption
Estimated Time:45s
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Topics

Environmental Impact and Fuel Efficiency

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