Generally, a driver should allow a minimum of 300 to 500 feet between his vehicle and an emergency vehicle in front of him. The amount of space that must be allowed between an emergency vehicle and a vehicle following may vary slightly from state to state.
When approaching a stopped emergency vehicle with its lights on, a driver must slow down and change lanes to leave the lane that's closest to the emergency vehicle open and vacant. If that is not possible, he must slow his vehicle significantly. If a police officer, traffic officer or firefighter is directing traffic, drivers must yield to that direction even when it conflicts with traffic signs or existing laws.