What is the minimum distance a vehicle may need to be driven before emissions testing?

The minimum distance a vehicle may need to be driven before emissions testing is based on the principle of ensuring that the vehicle's engine has reached optimal operating conditions. Driving a vehicle for a sufficient distance allows the engine to warm up fully, which can result in more accurate readings during emissions testing. The correct answer is 100 miles; this distance ensures that all systems, including the catalytic converter and oxygen sensors, have properly cycled and are functioning effectively. Such pre-testing driving can help avoid false failures during an emissions test due to incomplete combustion or other temporary issues related to cold starts or insufficient warm-up periods.