Final answer:
A sign stating 'EXEMPT' typically means that the vehicle is exempt from the legal requirement to stop at a railroad crossing unless a train is approaching. It also reflects historic exemptions provided by draft boards based on health, occupation, and family responsibilities.
Step-by-step explanation:
A sign with a white background and black letters that says 'EXEMPT' typically indicates that vehicles, such as buses or trucks from a transit system, are exempt from stopping at a railroad crossing unless there is a clear indication that a train is approaching. This contrasts with the usual requirement where certain types of vehicles must stop at all railroad crossings to ensure safety. The concept of exemption also applies to draft boards historically, where individuals could be granted exemptions from military service based on various criteria such as health, the wartime value of their civilian occupation, and home responsibilities .