Many permits are for oversize (overheight or overwidth) loads. The routing of these loads usually depends on data contained in the Bridge Inspection Management System. These types of loads do not normally require a structural evaluation of the affected bridges unless the weight and axle load distribution is such that an overweight permit may also be required

The Bridge Inspection Management System gives the values for available clearances as Items 51 (Roadway Width), 52 (Deck Width), 53 (Vertical Clearance over Roadway), 54.2 (Vertical Clearance Under Bridge), 55 (Lateral Underclearance on Right), and 56 (Lateral Underclearance on Left). These items taken together usually give sufficient information to define the limits for the passage of overheight and overwidth vehicles.

The permit investigator, District Permit Officer, or District Bridge Inspection Coordinator can quickly access the Bridge Inspection Management System to determine if the proposed route is capable of handling the proposed overwidth or overheight load. Truss bridges are particularly of concern for both these types of loads since many are in the 18- to 22-foot width range, and vertical clearance to the portals is often less than normal current design clearances.

The Bridge Inspection Management System gives vertical clearances to the least inch of clearance over the roadway, including shoulders rounded down to the nearest inch. The posted clearance signs are normally 3 inches less than this value. The clearance symbols maintained on the TxDMV permit maps are rounded down to the next 6 inches below the posted clearance. For instance, if the actual recorded clearance is 14-ft 2-in., the clearance sign is 13-ft 11-in., and the permit maps show the maximum available clearance as 13-ft 6- in. Occasional overheight loads can therefore be permitted for heights slightly over the limits given in the TxDMV permit maps provided there is close coordination between the district and the owner and pre-move specific measurements taken.

Normally, overwidth permits are granted simply on the basis of available Roadway Width (the clear distance between curbs or railings). If the overwidth load is configured such that the load will adequately clear bridge railings, then moves may be granted for loads significantly wider than the Deck Width. This requires the careful cooperation of all concerned parties including escort vehicles and traffic control. Damage and or removal of signs and delineators may occur for some overwidth permits. TxDOT personnel should ensure that all such temporary changes are corrected immediately after the permit load has passed.

More information on oversize permit requirements and procedures is given on the Texas Department of Motor Vehicles – Motor Carriers website at .