No police officer is present, and the driver suspects the crossing signal is malfunctioning. What should the driver do, and what must the driver confirm before crossing a passive crossing with no signal at all?

49 CFR § 383.123(a)(2)(iii); AAMVA CDL Manual Section 10.4.4, p.10-8

A malfunctioning signal can fail in either direction, showing danger when none exists or showing safety when a train is actually coming, so a driver's guess is not a safe substitute for guidance. At crossings with no signal at all, the driver's own sight distance is the only safeguard, which is why route planning for visibility is treated as part of the safety procedure, not an afterthought.