Section 5: Legal Loads and Load Posting
Anchor: #i1005897Definition of State Legal Loads
State Legal Loads may safely use any of our highways and bridges. Some routes and many bridges must be load-posted to protect them from possible damage. At this time, a load capacity of HS-20 is considered to best represent the State Legal Load for evaluation of the need for load posting.
Truck loads in Texas are considered legal if the gross load, axle load, axle configuration, length, and width are within the current size and weight laws or rules. The applicable laws are contained in the current volume of Texas Transportation Code.34 See Section 623.0111 of the Texas Transportation Code for permit fees for selected numbers of counties, and see Section 201.8035 for requirements related to the notification of off-system municipalities and counties of deficient bridges.
The laws also provide for additional rules and regulations regarding truck weights and configurations as may be formulated by the Texas Transportation Commission.
In general, the laws require that the maximum gross load on any truck cannot exceed 80,000 lbs, the maximum load on any pair of tandem axles cannot exceed 34,000 lbs, and the maximum load on any single axle cannot exceed 20,000 lbs. Total length must not exceed 65 feet and total width must not exceed 96 inches. However, in 1989 the Texas Legislature enabled truck owners to pay an annual fee to allow their gross legal loads to be increased by 5 percent with any individual maximum axle load increased by 10 percent.35 The bill was considered controversial because it allowed travel on any bridge, on- or off-system, even if it is load restricted. This portion of the Transportation Code was amended during the 77th Legislative Session to restrict vehicles possessing a permit of this type from crossing load restricted bridges unless the bridge is the only vehicular access.
There are other so-called legal loads, sometimes referred to as Bonded Trucks, such as ready-mix trucks, utility-pole trucks, garbage trucks, mobile cranes, oil well servicing equipment, etc., that have special rules passed by the legislature allowing special categories of loads and lengths exceeding the normal limits for trucks.
Most State Legal Loads do not have a greater effect on bridges than the current HS-20 design total gross load of 72,000 lbs even though they may have a total legal weight of 84,000 lbs.36 This apparent contradiction is due to the different axle load configurations and numbers of axles.
Anchor: #i1005939Load Posting
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. Posting may be at Operating Rating levels provided that the condition ratings exceed those defined in Figure 5-3 and Figure 5-4 and other requirements are met. Otherwise, if the Condition Ratings are less than those defined, the Posting must be at Inventory Rating levels.
All load postings of a given truck size actually mean that two trucks of the posted capacity to safely pass on the bridge. 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. 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.
Senate Bill 220, 77th Legislature, 2001, amended Transportation Code, Section 621.301, to provide 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.
The recommended load posting of all off-system bridges must be supplied to the affected municipalities and counties. TxDOT provides the necessary posting signs and placement hardware. Should the local jurisdiction elects not to post the bridge, there is the possibility that all federal funds could be jeopardized or delayed for all transportation-related projects, on- or off-system, in that county.
A list of off-system bridges that are recommended for load posting must be sent 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. Subsequently, after the appropriate load zone signs have been prepared by TxDOT, a letter is sent notifying the local jurisdiction as to where the signs, posts, and hardware may be picked up along with installation instructions. After the signs are installed, the local jurisdiction returns a statement of compliance to TxDOT.
Typical load posting signs are shown in Figure 5-5.37 Texas must comply with posting time limits, which are set by the Code of Federal Regulations. The time limit for initial or revised posting after bridge inspection is 90 days after the change in status for on-system bridges. This time limit is extended to 180 days for off-system bridges.38
Figure 5-3. On-System Load Posting Guidelines
NOTE: * Permit Loads will not be allowed on bridges that are load posted.
" If the bridge has not been rehabilitated or replaced in 24 months then the structure shall be closed.
I.F. - Inspection Frequency.
OR - Operating Rating (Item 64)
IR - Inventory Rating (Item 66)
Figure 5-4. Off-System Load Posting Guidelines
NOTE: * Permit Loads will not be allowed on bridges that are load posted.
If the bridge has not been rehabilitated or replaced in 24 months then the structure shall be closed.
I.F. - Inspection Frequency.
OR - Operating Rating (Item 64)
IR - Inventory Rating (Item 66)
Figure 5-5. Typical Load Posting Signs
Anchor: #i1006022Procedures for Changing On-System Bridge Load Posting
The following table outlines the procedure for changing the load posting of an on-system bridge.
|
Step |
Responsible Party |
Action |
|---|---|---|
| 1 |
District |
Complete Form 1083R, “Recommended Change in Bridge Load Zoning,” and send it to the Inspection Branch of the Bridge Division. If the request involves a new limit or a reduction of a current load limit, attach the most recent inspection report, plans (layouts and structural details), and any load ratings that support the recommended change. |
| 2 |
Bridge Division |
Review the request and supporting documents, and if review supports the recommended change, prepare a Minute Order for Commission approval based on the review. |
| 3 |
Bridge Division |
Provide approval notification and a copy of the approved Minute Order to the District. |
| 4 |
Bridge Division |
Notify the Motor Carrier Division of any bridge load restriction Minute Orders approved by the Commission. |
| 5 |
District |
On receipt of an approved Commission Minute Order, immediately erect signs indicating the proper load limit. |
| 6 |
District |
Notify the Bridge Division of the date that the sign was erected. |
Under the following conditions, the District should submit a completed Form 1083R showing reasons for a restriction removal to the Bridge Division’s Inspection Branch:
- Repair or rehabilitation of a bridge that increases load capacity and eliminates a load restriction.
- Construction of a new bridge that replaces one with a load restriction.
Procedures for Emergency On-System Bridge Load Posting
The following table outlines the procedure for changing the load posting of an on-system bridge in an emergency.
|
Step |
Responsible Party |
Action |
|---|---|---|
| 1 |
District |
Notify the Bridge Division’s Inspection Branch by telephone that an emergency load restriction is required. Identify deficiencies that justify the placement of an emergency load limit. |
| 2 |
Bridge Division |
Work with the District to determine the load limit, if required, and verbally authorize an emergency load restriction for a period not to exceed 60 days if necessary. |
| 3 |
Bridge Division |
Prepare a letter to the District for signature by the Director of the Bridge Division authorizing the temporary load limits and specifying the duration of the temporary limit. |
| 4 |
Bridge Division |
Verbally notify the District of official approval of the emergency load limit. |
| 5 |
Bridge Division |
Notify the Motor Carrier Division of any bridge load restriction. |
| 6 |
District |
On receipt of verbal approval by the Bridge Division, immediately erect signs indicating the emergency load limit. |
If the emergency load limit is required for a period longer than 60 days, the District should submit a request to the Bridge Division for the emergency load restriction to remain in place for another 60 days. If the bridge is not replaced or repaired before the emergency load restriction extension expires, the District should submit a request to the Bridge Division for a permanent load restriction following the procedures for changing on-system bridge load postings.
Anchor: #i1006061Closure of Weak Bridges
A memo to all District Engineers titled “Closing of Weak Bridges”39 from C.W. Heald dated Feb 12, 1999, contains procedures to be followed in Texas for the closure of bridges. Bridges with less than an HS-3 Operating Rating capacity must be closed according to the Texas Load Posting Guidelines presented in Figure 5-3 and Figure 5-4. These policies must be followed for on-system bridges and are strongly recommended for the municipalities and counties with jurisdiction over off-system bridges. Bridges with Inventory Ratings less than HS-3 but with Operating Ratings greater than HS-3 may remain open for a limited amount of time. If it is desired to leave a bridge in this category open, then the inspection frequency must not exceed six months and the bridge must be categorized for Priority 1 rehabilitation or replacement funding. Categorized Priority 1 means that funds are allocated for rehabilitation or replacement. This categorization is explained more fully in the section of Chapter 7, Texas Eligible Bridge Selection System. If after 24 months the bridge has not been rehabilitated or replaced, then it should be closed.
Anchor: #i1006076Off-System Bridge Closure Procedures
If inspection reveals deterioration that affects an off-system bridge’s ability to safely carry vehicular traffic, the department may use the following procedure to recommend that it be closed for safety reasons:
|
Step |
Responsible Party |
Action |
|---|---|---|
| 1 |
Bridge Division |
The Bridge Division will immediately notify the district if it determines that a bridge should be closed based on the results of an inspection conducted by the Bridge Division. |
| 2 |
District |
The district will verify as soon as possible the condition of a bridge recommended for closure by a consultant. |
| 3 |
District |
The district will immediately notify the local entity of a valid closure recommendation. The district will inform the local entity that its participation in the TxDOT Participation Waived and Equivalent Match Program depends on full compliance with departmental closure and posting recommendations and that failure to follow closure recommendations could result in the loss of federal funds. The district will promptly update the Bridge Inspection database to reflect the closure recommendation. (See Item 41 in the file titled “coding_guide.)” NOTE: The department will not conduct another formal inspection of the bridge until it is repaired or replaced. |
| 4 |
Local Entity |
The local entity will close the bridge and notify the district when the bridge is closed to traffic. |
| 5 |
District |
The district will verify closure of the bridge when it receives notification and will include a photo or certified documentation verifying the closure in the bridge inspection file. The district will promptly update the Bridge Inspection database to reflect the closure status of the bridge. (See Item 41 in the file titled “coding_guide.”) |
| 6 |
District |
If the bridge will remain closed for an extended period of time, the district will verify and document with a photo that the bridge is still closed to traffic as part of the regular inspection cycle. |
34. Texas Transportation Code, Title 7, Chapter 621.
35. Texas Transportation Code, Section 623.011.
36. Texas Transportation Code, Section 623.011.
37. Texas Manual on Uniform Traffic Control Devices, 1980
38. “Closing and Posting Recommendations for Off-System Structures,” Memo from Robert L. Wilson, P.E., TxDOT, October 1997
39. Closing of Weak Bridges, Memo from C.W. Heald, P.E., TxDOT, February 1999.