When approaching a railroad crossing, which of these safety precautions applies?

Do not rely solely upon the presence of warning signals, gates, or flagmen to warn of approaching trains.
DO NOT shift gears while crossing railroad tracks.
Double tracks require a double check. A train on one track may hide a train on the other track. Look both ways before crossing. After one train has cleared a crossing, be sure no other trains are near before starting across the tracks.
Never permit traffic conditions to trap you in a position where you have to stop on the tracks. Be sure you can get all the way across the tracks before you start across.