You see an emergency vehicle with flashing lights stopped ahead. What must you do?

Explanation

Under Washington State's Move Over Law, to pass an emergency vehicle, tow truck, or other roadway assistance vehicle that is stopped with its lights flashing, you must move into a non-adjacent lane if possible, leaving at least one vacant lane between you and the vehicle. If this is impossible (no other lanes in your direction) or unsafe, you must slow down until you have passed the vehicle. (Note: All US states now have their own Move Over Laws, but some of them require drivers to do different things. When traveling out of state, always check the local traffic laws.)