I can find no regulations on the double decker bus in the USA.
United States
A Van Hool US-specification double-decker bus demonstrating in New York City
In Davis, California, Unitrans, the student-run bus company of University of California, Davis, operates six double-decker buses imported from London. One of these buses has been converted to run on compressed natural gas (CNG) . There was also the prototype GX-1 Scenicruiser of Greyhound Lines, which enters from the first floor: the second floor contains the driver's compartment and more seats.
Citizens Area Transit, the transit authority in the Las Vegas, Nevada area, introduced a fleet of double-deckers to serve the Las Vegas Strip route in October 2005. The route is branded as "The Deuce". As of 2009 it serviced eight lines.
In Snohomish County, Washington, Community Transit operates one Alexander Dennis Enviro500 double-decker bus as a demonstrator, which rotates among commuter routes between Snohomish County and Seattle. A fleet of 23 such buses have been purchased for service beginning 2010.[15]
In San Luis Obispo, California, SLO Transit tested a double-decker bus in late 2008 to see if it would alleviate the over-crowdedness of Route 4. The borrowed bus has been returned, and SLO Transit has purchased one double-decker bus of its own using a combination of Federal, State and local funding. The bus went into operation on September 8, 2010.[16][17]
In Los Angeles County, California, the Antelope Valley Transit Authority uses double-decker buses as part of its commuter service to the Los Angeles area.[18]
Also in Los Angeles, SCRTD used Neoplan AN 122/3 Skyliners double-decker buses from the late 70s until 1993.
In San Francisco, California, the San Francisco Municipal Transportation Agency operated one Alexander Dennis double decker bus as a demonstrator between December 12, 2007 and January 8, 2008.[19] The bus was running on some high capacity routes as trial.[20]
Also, in the United States, a private operator, Megabus, run by Coach USA, employs double-decker buses on its busier intercity routes.
Finally, starting in 2013 Stallion Bus will start distributing open top and closed top double deck buses to the United States and Canada [21