The GM TDH-4801 & TDM-4801 were a special series of GM "old-look" transit buses that were produced between 1953 and 1958 and which were designed to maintain a maximum rear axle weight load of no more than 16,500 pounds. The reason for this was due to a requirement in California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

 at the time that buses more than 35 feet (10.7 m) in length or 96 inches (2.4 m) in width could only be operated under special authorization from the California Public Utilities Commission (CPUC)

California Public Utilities Commission

The California Public Utilities Commission is a regulatory agency which regulates privately owned public utilities in the state of California, including electric power, telecommunications, natural gas and water companies...

, and the CPUC had denied authorization for the TDH-5105 (a 40 feet (12.2 m), 102 inches (2,590.8 mm) bus) partially due to its weight. Both the TDH-4801 and TDM-4801 have an unusual vehicle length of 37¾ feet (rather than the normal 35 or 40 feet) and a seating capacity of only 48 (rather than 51 for a comparable 40 feet (12.2 m) bus). Both models are 102 inches (2.6 m) wide. The TDH-4801 was equipped with an automatic transmission

Automatic transmission

An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...

 and 547 were built between 1953 and 1958. The TDM-4801 was equipped with a manual transmission

Manual transmission

A manual transmission, also known as a manual gearbox or standard transmission is a type of transmission used in motor vehicle applications...

and 75 were built in 1954.