King County Road Services - Frequently-asked questions

A bridge load rating is the measure of a bridge's load carrying capacity. National Bridge Inspection Standards (NBIS) require the posting of load limits on a bridge, if a legal load configuration exceeds the operating rating for that bridge. The bridges are posted for AASHTO trucks Type 3, Type 3S2 and Type 3-3 which are intended to encompass the majority of loads to which a bridge might be subjected. A list of posted bridges with their corresponding load limits can be found on the Bridge Unit's Web site.

A bridge load rating is the measure of a bridge's load carrying capacity. There are two capacity levels, the Inventory Rating and the Operating Rating. The Inventory Rating is the load that a bridge can carry for an indefinite number of loading cycles without detriment to the bridge. The Operating Rating is the maximum load that can be carried on an infrequent basis without detriment to the bridge. The bridges are posted with a load limit between the Inventory Rating and the Operating Rating.

Visit the Bridge Unit Web site to learn more.

To request the schedule for bridge maintenance, please contact the Road Services Division's Engineering Section.

As a general rule of thumb, if the bridge load limit is posted or your truck's weight exceeds the maximum legal load, you should apply for a permit. If your truck configuration matches the posted truck not exceeding the maximum amount allowed gross vehicle weight, then you may proceed without a permit. Please visit the Bridge Unit Web site for information on getting an overlegal load permit for use on King County-owned bridges.