49 U.S.C. § 31113 — Width limitations

(a) General Limitations. Except as allowed under (e), a state other than Hawaii cannot make or enforce a rule that sets a width limit other than exactly 102 inches for a commercial vehicle on: an interstate highway segment, unless exempted under (e); a qualifying federal-aid highway the Secretary designates, with lanes at least 12 feet wide; or a qualifying federal-aid highway the Secretary designates as consistent with highway safety. Despite that, a state can keep enforcing a width rule it already had in effect on April 6, 1983, for vehicles wider than 102 inches, until it adopts a new rule that follows this section. A federal-aid highway other than an interstate that was not already designated under this section by June 5, 1984, can only be added later with that state's chief executive agreeing to it. (b) Exclusion of Safety and Energy Conservation Devices. When measuring width, you do not count a safety or energy-saving device the Secretary decides is necessary for safe, efficient operation. (c) Special Use Permits. A state can issue a special permit letting a commercial vehicle wider than 102 inches operate. (d) State Enforcement. Consistent with this section, a state can enforce the 102-inch width limit on interstate segments, except exempted ones, or other qualifying federal-aid highways the Secretary designates. (e) Exemptions. A state's chief executive, after consulting local governments and any affected neighboring state about possible alternate routes, can ask the Secretary to exempt an interstate segment from the 102-inch rule, allowing a narrower limit — but not for buses — on that segment, if it cannot safely handle 102-inch-wide vehicles. The request needs specific safety evidence and a description of the consultations. The Secretary — from a request or on the Secretary's own initiative — must grant the exemption after considering alternate routes, if the Secretary agrees the segment cannot safely handle it. The Secretary must decide within 120 days of the request or of starting the review, whichever applies; if the deadline will be missed, the Secretary must tell Congress why, what resources are assigned, and the expected decision date. The Secretary must give the public notice and a chance to comment before deciding. An exemption granted before the final regulations under (a) are issued gets folded into those regulations; one granted afterward gets published as an amendment.