At railroad crossings that are only marked with a stop sign, you must stop and then proceed only when

Explanation

At crossings marked with automatic flasher units or automatic crossing gates, you must stop if the lights are flashing or the gates are lowered, and you must remain stopped until the lights stop flashing and the gates are raised. At crossings that are only marked with a stop sign, you must stop and then proceed only when you determine that no train is approaching, no pedestrians are approaching, and it is safe to cross.