1.    When a vehicle approaches a railroad grade crossing under any of the circumstances stated in this section, the driver of the vehicle shall stop within fifty feet [15.24 meters] but not less than fifteen feet [4.57 meters] from the nearest rail of such railroad, and may not proceed until the driver can do so safely. These requirements apply when:

a.    A clearly visible electric or mechanical signal device gives warning of the immediate approach of a railroad train or other on-track equipment; b.    A crossing gate is lowered or when a human flagman gives or continues to give a signal of the approach or passage of a railroad train or other on-track equipment; c.    A railroad train or other on-track equipment approaching within approximately one thousand three hundred twenty feet [402.34 meters] of the highway crossing emits a signal audible from such distance and such railroad train or other on-track equipment, by reason of its speed or nearness to such crossing, is an immediate hazard; or

d.    An approaching railroad train or other on-track equipment is plainly visible and is in hazardous proximity to such crossing.

2.    A person may not drive a vehicle through, around, or under any crossing gate or barrier at a railroad crossing while the gate or barrier is closed or is being opened or closed. A person may not drive a vehicle past a human flagman at a railroad crossing until the flagman signals that the way is clear to proceed.