No federal regulation sets a drawbridge procedure for commercial drivers; the practice comes from the CDL manual and from state law. What does that practice call for a bus driver to do at a drawbridge?

Explanation

The practice is to stop at least 50 feet before the draw and look to confirm the draw is completely closed, except where a signal light shows green or an attendant or traffic officer controls traffic when the bridge opens, in which case the driver slows down and confirms it is safe rather than stopping. The stop exists because an open or partly open draw is not something a driver can judge reliably at speed, and the exceptions exist because a green light or a human controller has already made that check. This is bus-driver practice from the manual and from state law, not a federal rule: 49 CFR Part 392 was checked directly and contains no drawbridge provision at all, and 49 CFR 383.117(a)(4) names proper procedures at drawbridges as a required knowledge area for this endorsement without stating any procedure, which is the only federal footing the subject has. The wrong options either remove the exceptions, borrow the 15-to-50-foot stopping window that 49 CFR 392.10 sets for railroad crossings and that does not apply here, or assume barriers make the driver's own check unnecessary.

Source: 49 CFR 383.117(a)(4)