What is crucial to maintaining a safe distance from the vehicle ahead?

Observing the brake lights of the vehicle ahead is crucial for maintaining a safe following distance because it allows you to anticipate the actions of that vehicle. When the brake lights illuminate, it's an indicator that the driver is slowing down or stopping. By noticing this early, you can adjust your speed accordingly to maintain a safe distance and prevent rear-end collisions.

While checking mirrors can provide useful information about surrounding traffic, it does not specifically alert you to changes in speed of the vehicle directly in front of you. Additionally, looking at your speedometer helps maintain your speed but does not give you information about the action of the vehicle ahead. Lastly, using peripheral vision can assist in observing surrounding vehicles, but it does not provide specific information about when the vehicle ahead is about to stop or slow down. Therefore, being attentive to brake lights is the most effective way to ensure you're maintaining a safe distance from the vehicle in front of you.