The decision to proceed at a passive railroad crossing:

Passive Crossings does not have any type of traffic control device. You must stop at these crossings and follow proper procedures. However, the decision to proceed rests entirely in your hands. Passive crossings require you to recognize the crossing, search for any train(s) using the tracks, and decide if there is sufficient clear space to cross safely. Passive crossings have yellow circular advance warning signs, pavement markings, and crossbucks to assist you in recognizing a crossing. [Commercial Driver Handbook]