TRB Special Report 267: Regulation of Weights, Lengths, and Widths of Commercial Motor Vehicles is critically evaluated. It is an important, congressionally mandated report that contains a series of conclusions and recommendations regarding truck size and weight (TS&W) regulations in the United States. The report concludes that increases in TS&W limits have great potential for increasing freight market efficiency but that safety and other effects are not well understood. To facilitate the liberalization of TS&W limits, the report recommends a revised regulatory regime that would involve federal supervision of state-set limits, with evaluation provided by an independent Commercial Traffic Effects Institute. This evaluation argues that the report focuses too narrowly on trucking efficiency and overlooks transportation efficiency. This narrow analytical perspective significantly limits its usefulness in establishing national transportation policy. Also, there is no analytical basis for the report's most important conclusions and recommendations, either in the report or in earlier TS&W studies evaluated by the Committee for the Study of the Regulation of Weights, Lengths, and Widths of Commercial Motor Vehicles.