If you must drive below 40 mph on a limited-access highway in Pennsylvania, use _________ to warn the drivers behind you.

Explanation

Before you turn, change lanes, or slow down, warn other drivers well in advance. If you must drive below 40 mph on a limited-access highway in Pennsylvania, use your hazard (four-way) flashers to warn the drivers behind you. (Note: In some other states, it's illegal to use hazard flashers while you're driving. Before slowing down, you can tap your brake pedal a few times to flash your brake lights instead. Whenever you travel out of state, always check the local traffic laws.)