By Ralph K. Banks, P.E.
Lone Star LTAP, TEEX Adjunct Instructor
All bridges, defined as bridge classified roadway structures, located on the public highways, roads and streets of the Lone Star State are required by the federal government under National Bridge Inspection Standards to be inspected by pre-qualified bridge inspectors every two years. The state agency responsible for carrying out this federal requirement in Texas is the Texas Department of Transportation (TxDOT) Bridge Division and District offices. Included in the inspection program are not only all bridges located on designated highway routes of the state highway system, but all other such structures of the state located on public streets and roads under the jurisdiction of cities, counties and special districts, which are referred to as “local jurisdiction bridges.”
An integral part of these inspections is an engineering determination of the safe load capacity of each bridge. For local jurisdiction bridges found to be incapable of safely carrying maximum legal loads of the state, TxDOT recommends to the appropriate local jurisdiction that restriction load postings be made. Appropriate load posting signs with support posts are provided free of charge to the local jurisdiction, with the signs expected to be promptly erected by the local jurisdiction at the jurisdiction’s expense.
Periodically, about once a year, the federal government through the Federal Highway Administration (FHWA) reviews the Texas Bridge Inspection Program and notes deficiencies. FHWA reviewers are frequently noting that some of the local jurisdiction bridges in Texas that should be load posted are not load posted; the FHWA records each of these instances as “non-compliance” items for Texas.
For each bridge, including local jurisdiction bridges, TxDOT maintains a computerized inventory data file that contains an item of data indicating whether or not the bridge is recommended for load posting. Any bridge found by the FHWA that has been recommended for load posting for as much as or longer than 180 days but has not been load posted is assessed as a non-compliance item for which TxDOT is expected to “take action” to resolve.
In Texas, except for certain exempt vehicles, the statutory maximum loadings that may be carried on the public highways, roads and streets are 20,000 pounds for single axles, 34,000 pounds for tandem axles, and 80,000 pounds gross for individual vehicles. The statute further provides that the 80,000-pound gross legal load may be distributed over a length according to a formula specified in the statute. Therefore, under this system of axle and gross load limitations, the entire population of Texas bridges with the great number of structure types and span lengths (short and long) are addressed in terms of these three loadings, with appropriate load limits assigned.
Single or tandem axle load limitations usually apply only to “short” spans that are just long enough for the loaded single or tandem axle of a legal vehicle to fit on it. Gross vehicle load limitations usually apply to span lengths or continuous units that are long enough for the entire longer legal vehicle to fit on it at one time.
In summary, any part of a given bridge structure on the public highways, roads and streets of Texas that is found to be incapable of safely carrying any one or more of these maximum legal loadings results in that bridge being recommended for one or more load limit postings for single axle, tandem axle and/or gross load.
In the absence of an appropriately posted sign to the contrary at a bridge, a driver has a right to expect the vehicle he/she is operating across the bridge that does not exceed any of the usual state maximum legal loadings can safely pass. If in the absence of such a sign the bridge does collapse under the vehicle, the appropriate responsible jurisdiction is surely answerable.
Accordingly, responsible local jurisdictions are asked to promptly load post any bridges identified by TxDOT as needing such posting, and to keep those postings maintained, all for the benefit of public.