RSPA is extending the time period, from August 31, 1993 to April 21, 1994, during which cargo tank motor vehicles may continue to be constructed to MC 306, MC 307, MC 312, MC 331, and MC 338 specifications. The extension is based on-requests from the Cargo Tank Manufacturing Association, the Truck Trailer Manufacturers Association, the Heil Co., and members of the Compressed Gas Association. This action will allow additional time for RSPA and industry to resolve certain technical issues concerning the. manufacture of cargo tank motor vehicles to the recently adopted DOT 406, DOT 407 and DOT 412 specifications and to resolve certain concerns on the structural integrity calculations in the MC 331 and MC 338 specifications.