Rules 9.2.5 and 9.2.6:  To ensure that there is adequate support provided for the decking, these rules requires that the "inner edge of the outermost decking support surface on each side of the bridge must be more than 1' 6.1/2" " and that the "outer edge" of the same support must not be less than 1' 3" from the centerline.  These clearance requirements are required over the entire length of the bridge.  These dimensions are measured from the centerline required by rule 9.4.  See the "Decking Support" detail, detail C, on the "Site and Bridge" diagram, Exhibit 1 of the rules.

Common Error:  In some cases, designers have failed to provide adequate support for the decking by placing the decking supports too close together or too far apart.  This leads to a condition where the decking cannot be safely supported.  If judges deem that the loading the bridge is unsafe due to marginal support, the bridge may be disqualified under rules 5 or 12.1. Also note that the paragraph at the head of section 9 states that "the bridge may not be modified nor distorted from its as-built condition in order to satisfy dimension and support rules."