Which policy represented tightened vehicle emission standards in the United Kingdom?

• A. Loosened emission standards for vehicles
• B. Banned all cars from cities
• C. Tightened emission standards for vehicles
• D. Encouraged diesel engines

Answer: (C)

Emissions standards set the maximum amount of pollutants that a vehicle can emit. When those standards are tightened, the allowed limits become more strict, nudging manufacturers to use cleaner technologies and fuels to meet the new rules. In the United Kingdom, a policy that tightens vehicle emissions means introducing stricter limits for pollutants like NOx and particulate matter, often aligning with or surpassing EU Euro standards and related national air-quality measures. This is the mechanism that reduces urban air pollution from cars and vans over time.

The other options describe actions that would not reduce emissions: loosening standards would let more pollution slip through, banning all cars from cities is an extreme, impractical measure, and encouraging diesel engines would typically lead to higher emissions of certain pollutants unless accompanied by new controls, which is not tightening.