Our church owns a small bus that has 18 seats. While the bus is used mostly for local transportation, we occasionally use it for out-of-town trips. Some of these trips go across state lines. Some members of our church have asked if the bus needs to be certified by the U.S. Department of Transportation and display a Department of Transportation sticker. Does it?
Any vehicle designed to carry more than 15 passengers (including the driver), that is used across state lines, and that does offer transportation services for hire, is a "private motor carrier of passengers" (PMCP) subject to Federal Motor Carrier Safety Regulations (FMCSRs). Even if you do not operate your bus in interstate commerce, you may still be subject to state regulations similar to the FMCSRs.
As a private motor carrier of passengers, your vehicle will fall into one of two groups: business or non-business. In most cases, church-owned PMCPs are non-business, meaning that you provide private, interstate transportation of passengers that is not in the furtherance of a commercial enterprise. The Department of Transportation lists "churches, scout groups and other charitable organizations that may purchase or lease buses for the private transportation of their respective groups" as examples of non-business PMCPs.