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Questions and Answers About Vehicle Size and Weight

23 CFR 658.9 National Network Criteria

23 CFR 658.9 National Network Criteria

Must traffic lanes on the National Network be 12 feet wide?

A traffic lane on the National Network (NN) is required to be designed to have a width of 12 feet or more or be otherwise consistent with highway safety [see 23 CFR 658.9(b)(5)]. There are several tools and methodologies that can be applied to determine the safety and operational impacts of design decisions which include the Highway Safety Manual (HSM), the Highway Capacity Manual (HCM), and performance-based practical design

For portions of the NN that are also part of the NHS, design standards can be found in 23 CFR part 625. Guidance on NHS Design Standards and Design Exceptions are available at
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