Figure 3-3. Permitted Longer Combination Vehicles on the National Highway System: 2007
All states allow doubles consisting of a 28-foot semitrailer and a 28-foot trailer behind the tractor. Fourteen states and six state turnpike authorities allow longer combinations on at least some parts of the road network. Allowable routes for longer combination vehicles have been frozen since 1991.
Source: U.S. Department of Transportation, Federal Highway Administration, Office of Freight Management and Operations, Freight Analysis Framework, 2007.
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