23 CFR 658.9 - National Network criteria.
(b) For those States with detailed lists of individual routes in the appendix, the routes have been designated on the basis of their general adherence to the following criteria.
(1) The route is a geometrically typical component of the Federal-Aid Primary System, serving to link principal cities and densely developed portions of the States.
(2) The route is a high volume route utilized extensively by large vehicles for interstate commerce.
(3) The route does not have any restrictions precluding use by conventional combination vehicles.
(4) The route has adequate geometrics to support safe operations, considering sight distance, severity and length of grades, pavement width, horizontal curvature, shoulder width, bridge clearances and load limits, traffic volumes and vehicle mix, and intersection geometry.
(5) The route consists of lanes designed to be a width of 12 feet or more or is otherwise consistent with highway safety.
(6) The route does not have any unusual characteristics causing current or anticipated safety problems.
(c) For those States where State law provides that STAA authorized vehicles may use all or most of the Federal-Aid Primary system, the National Network is no more restrictive than such law. The appendix contains a narrative summary of the National Network in those States.