What does passenger-vehicle guidance say about fueling a bus with riders on board?

Explanation

Fueling a bus with riders aboard should be avoided unless there is no alternative, and it should never be done at all inside an enclosed building with riders aboard. Both parts of the guidance follow from the same hazard at two intensities: fuel vapor plus a vehicle full of people who cannot get out quickly is bad in the open and far worse in an enclosed space where vapor collects. 49 CFR 392.50 does set federal fueling precautions, including not fueling with the engine running except where necessary and no smoking or open flame near a vehicle being fueled, but it was checked directly and says nothing about buses or passengers, so no federal rule conditions fueling on riders being aboard and this practice is attributed to the manual under the catch-all at 49 CFR 383.117(a)(6). The wrong options misread the guidance in both directions, treating it as no restriction at all or as an absolute ban, and the last inverts it exactly, since an enclosed building is the one place refueling with riders aboard should never happen.

Source: 49 CFR 383.117(a)(6)