Section 31.27. Railroad grade crossings

(a) All motor vehicles shall, upon approaching any railroad grade crossing, make a full stop not more than 50 feet nor less than 15 feet from the nearest rail of the railroad grade crossing, and shall not proceed until due caution has been taken to ascertain that the course is clear.

(b) A full stop need not be made at the following:

(1) A street car crossing within a business or residence district of a municipality.

(2) A railroad grade crossing where a police officer or a traffic-control signal (not a railroad flashing signal) directs traffic to proceed.

(3) An abandoned or exempted grade crossing which is clearly marked as such by or with the consent of the proper state authority, when such marking may be read from the position of the driver.

(c) All such motor vehicles shall display a sign on the rear reading, ‘‘This vehicle stops at railroad crossings.’’