49 CFR Part 37 - Transportation for Individuals With Disabilities; Reasonable Modification of Policies and Practices

24. Unattended Passengers.

Where a passenger's request for assistance means that the driver will need to leave passengers aboard a vehicle unattended, transportation agencies should generally grant the request as long as accommodating the request would not leave the vehicle unattended or out of visual observation for a lengthy period of time, both of which could involve direct threats to the health or safety of the unattended passengers. It is important to keep in mind that, just as a driver is not required to act as a PCA for a passenger making a request for assistance, so a driver is not intended to act as a PCA for other passengers in the vehicle, such that he or she must remain in their physical presence at all times.