The Pennsylvania ADR Certificate of Compliance is a document issued by the Pennsylvania Department of Transportation (Penn DOT) as a requirement for certain vehicles to be operated on public roads in the Commonwealth of Pennsylvania. Depending on the type of vehicle, the Certificate of Compliance will require the vehicle to meet specific safety standards, including brake systems, suspension systems, fuel systems, and other safety components. There are three types of Pennsylvania ADR Certificate of Compliance: Class A, Class B, and Class C. Class A is for vehicles weighing up to and including 10,000 lbs., Class B is for vehicles weighing over 10,000 lbs., and Class C is for vehicles weighing over 26,000 lbs. Each Certificate of Compliance must be renewed annually or biennially, depending on the type of vehicle.