Load posting is often required for structures that, due to their original design or condition, do not have the structural capacity to safely carry the State Legal Loads. Posting is usually necessary for bridges designed at a time when the design truck for the particular stretch of roadway was only H-10 or H-15, meaning gross truck loads of 20,000 or 30,000 lbs. Structures may be posted at Operating Rating levels provided that the condition ratings exceed those defined in Figure 6-3 and Figure 6-5. and other requirements are met. Otherwise, if the Condition Ratings are less than those defined, the Posting must be at Inventory Rating level of the corresponding element (i.e. if the Condition Rating of the superstructure on a particular bridge is a 5, and the Condition Rating of the substructure is a 4, then the Posting is at the Inventory Rating level of the substructure, not the superstructure). Per the 2016 FHWA Memo of Load Rating for the FAST Act’s Emergency Vehicles, when a load rating results in an operating factor less than 1.0 for the emergency vehicles, the bridge shall be posted for the governing single axle, tandem axle and gross weight limits derived from the operating rating factors of EV2 and EV3. In addition, a unique load posting sign, R12-8nT, only for emergency vehicles shall be utilized.

A load posting of a given truck size means that two trucks of the posted capacity can safely pass on the bridge at the same time. This concept is often misinterpreted by those doing load ratings and making load posting recommendations. It is recognized that a bridge posted for an HS-5 (18,000 lbs. gross load) can safely carry a single truck of significantly more than 18,000 lbs. For a bridge with width at least 18 feet, no method ensures that only a single truck is on the bridge. Therefore, assume that two trucks of the same size could be passing on the bridge simultaneously.

However, some bridges, particularly off-system, are load posted assuming only one rating truck even though they may be wider than 18 feet. This condition usually occurs due to the volume of truck traffic, structure width or approach roadway width, striping, runners, etc., making them functionally one-lane bridges for trucks.

It is important to recognize that even though a bridge may have been designed to an H-15 loading, it may not need to be load posted due to considerations discussed previously, such as reinforcement or member size in excess of the theoretical amount, more liberal load distribution now used in analysis, and LF analysis methods which usually increase Inventory Ratings significantly more than the original design loading.

Transportation Code, Section 621.301 provides that a county may establish load limits for a county road or bridge only with the concurrence of the department. If a county determines that the load limit of a county bridge should be different than the load limit supported by a department inspection, the county must submit the proposed load limit to the district engineer. A request for a load limit must be accompanied by supporting documentation that is sealed by an engineer and that includes at a minimum: calculations supporting the proposed limit and a structural evaluation report documenting the condition of the bridge. The district engineer will give a concurrence to a county's proposal in writing. If the department does not indicate concurrence or non-concurrence in writing within 30 calendar days of receipt by the department of a request that included all required documentation, the proposed load limit must be deemed concurred with by the department. The department may review the load limit and withdraw this concurrence at any time by providing written notification to the county. A county may appeal the decision of the district engineer by submitting a written request along with the required documentation to the executive director. The executive director will review the request and determine if department concurrence will be granted. The executive director's decision is final.

Typical load posting signs are shown in Figure 6-6 Texas must comply with posting time limits established by FHWA. FHWA requires that bridge load posting signs be installed no later than 30 days after a load rating determines a need for such posting. When updated load ratings are required (or submitted by consultants), they are to be performed and submitted for TxDOT approval within 30 days following an inspection. TxDOT will act promptly on all load posting recommendations made affecting public safety. Otherwise, TxDOT will review and approve load ratings for on-system bridges within 90 days of the date of inspection, or when a change is identified that warrants a re-rating. Approval of all off-system load ratings and load posting recommendations, except those for Emergency Vehicles, will be made when inspection reports are approved by TxDOT (within 90 days of the inspection date). All Emergency Vehicle load ratings and load postings need to be reviewed and approved by TxDOT Bridge Division.

District bridge offices send a list of off-system bridges that are recommended for load posting by certified mail to the owner of the bridges. A signed copy of the cover letter is returned to TxDOT from the local jurisdiction official. After the appropriate load zone signs have been prepared by TxDOT, district bridge office sends a letter notifying the local jurisdiction as to where the signs and hardware may be picked up along with installation instructions. TxDOT supplies materials to implement the recommended load posting of all off-system bridges to the local jurisdiction. After the signs are installed, the local jurisdiction returns a statement of compliance to TxDOT. Photographs are required to document installation of load restriction signs and are stored in the inspection file for historical reference. When local governments fail to install load posting signs within one week of the 30-day timeframe, Districts will need to take further action to ensure that signs are installed as authorized under Texas Transportation Code §201.8035.(c).

Attention should be given to bridges on Farm to Market and Ranch to Market roads where gross load postings of 58,420 lbs. are present. This load restriction only applies to older pavements of light design and is independent of the bridges. All bridges in Texas must be analyzed to determine load carrying capacity. Furthermore, the load restriction shall not be reflected in the coding in the Bridge Inspection Management System. If these signs appear in photographs that are part of a bridge inspection, a notation should be added to reduce confusion as to the purpose of the weight restriction.