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Application of Design Standards, Uniform Federal Accessibility Standards, and Bridges

Contact information was updated by Vertical Clearance Memo on 4/15/09.

Formerly Federal-Aid Policy Guide Non-Regulatory Supplement, NS CFR 23 625
March 1, 2005, Transmittal 33
See Order 1321.1C FHWA Directives Management

This supplement includes information on application of design standards, uniform federal accessibility standards, and bridges

  1. National Highway System. Section 109(c) of Title 23, United States Code (U.S.C.), provides that design and construction standards for new construction and reconstruction on the National Highway System (NHS), and for resurfacing, restoring, and rehabilitating multi-lane limited access highways on the NHS, shall be those approved by the Secretary in cooperation with the State highway departments. In a similar manner, 23 U.S.C. 109(b) provides standards for the Interstate system. The term "multi-lane limited access highway" in 23 U.S.C. 109(c) means Interstate or other freeway with full control of access. Standards for the design and construction of all projects on the NHS, including the Interstate system, are applicable to any proposed improvement regardless of the funding source (Federal, State, local or private). The standards are for the National Highway System, rather than for Federal-aid projects on that system. Deviations from the standards must have approved design exceptions.

    1. Interstate System Projects. In accordance with 23 U.S.C. 109(b), the current AASHTO Interstate standards and policies as incorporated in 23 CFR 625 are applicable. Those standards apply whether or not the State has chosen to use the exemption provisions of 23 U.S.C. 106(b). Also, there is no authority under the ISTEA to develop FHWA approved individual State 3R standards for Interstate projects.

    2. Non-Interstate System Projects

      • (1) New construction and reconstruction: In accordance with 23 U.S.C. 109(c), the current AASHTO standards and policies as incorporated in 23 CFR 625 are applicable to new construction and reconstruction. In addition to the Interstate system, the NHS consists of other principal arterials, including non-Interstate freeways. Therefore, those parts of the AASHTO Policy on Geometric Design of Highways and Streets (Green Book) applicable to highways classified as principal arterials, including non-Interstate freeways, must be used. Generally, the criteria in the Green Book functional chapters on local roads and streets and on collectors are not applicable to projects on the NHS. However, if highway segments functionally classified less than principal arterials are incorporated in the NHS because they connect to intermodal facilities or serve defense needs, the standards used may be those appropriate for the functional classification, including military requirements, of the segment taking into account the type of traffic using the segment.

      • (2) For 3R projects: All 3R projects, other than on the Interstate System or other freeways, may be constructed in accordance with FHWA-approved AASHTO standards for new and reconstruction projects or in accordance with FHWA-approved individual State standards developed pursuant to 23 U.S.C. 109(o) and 23 CFR 625.

      • (3) Certification acceptance projects: Standards for projects under certification acceptance procedures are those identified and approved in accordance with 23 CFR 640.

    3. Certification. For projects on the NHS under the exemption provision of 23 U.S.C. 106(b)(1), the State certification that "...all work will meet or exceed the standards approved by the Secretary under section 109(c)" must be done on a project-by-project basis. Title 23 U.S.C. 109(c) applies to new construction, reconstruction and to multilane limited access (freeway including Interstate) 3R projects on the NHS. For non- freeway 3R projects the certification should be based on meeting the FHWA approved 3R standards developed under 23 U.S.C. 109(o) and 23 CFR 625. The form of the certification should be agreed upon between the Division office and the State.

  2. Non-National Highway System. As provided in 23 U.S.C. 109(p), there will be no federally required or approved standards for Federal-aid projects off the NHS regardless of the funding source. Non-NHS projects are to be "designed, constructed, operated, and maintained in accordance with State laws, regulations, directives, safety standards, design standards, and construction standards." While there is no direct applicability of the safety provisions of 23 U.S.C. 109(o) or the historic and scenic values provisions of 23 U.S.C. 109(q) to non-NHS projects, the States are strongly encouraged to consider and apply these provisions in developing and applying their non-NHS standards.

  3. Projects with Historic and Scenic Impacts or Values. Title 23 U.S.C. 109(q) deals with the application of design standards on projects which involve or are located in areas of historic or scenic value. The intent is to emphasize that a great deal of flexibility can and should be used in design and construction of such projects. Because each scenic or historic site or area is unique, development of national standards for such projects is not appropriate. The intent of this section should be considered in the development of all Federally funded projects but is required to be considered in the design of NHS projects funded under 23 U.S.C. 103(e)(4), Interstate Substitute Program; 23 U.S.C. 133, Surface Transportation Program; or 23 U.S.C. 144, Highway Bridge Replacement and Rehabilitation Program.

  4. Safety Enhancement

    1. Title 23 U.S.C. 106(b)(3) provides that safety enhancement on 3R projects on the NHS and on any low cost (less than $1 million estimated construction cost) projects on the NHS may be accomplished using phase construction. That is, those safety considerations that are reflected in an operative Safety Management System (established and implemented in accordance with 23 U.S.C. 303) and which do not present an immediate potential hazard as the result of the proposed improvement, may be met by phased construction. However, until such safety management system is in effect, the general safety requirement of existing 23 U.S.C. 109(a) and the safety enhancement provisions of 23 U.S.C. 109(o) are applicable to projects on the NHS.

    2. Preventive maintenance projects (joint repair, pavement patching, crack sealing, bridge painting, etc.) using Federal-aid funds on Interstate highways and similar minor work on other NHS highways may be approved by FHWA without including safety or geometric enhancements. However, such approvals are to be given with the understanding that appropriate safety and geometric enhancements will be an integral part of future 3R/4R projects. Further, preventive maintenance or minor work items performed in this manner must not degrade any existing safety or geometric aspects of the facility.

  5. Design Speed

    1. For all new and reconstruction projects, and all Interstate System projects, the geometric design should be consistent with speed implied to the driver by the posted or regulatory speed. Therefore, the design speed chosen for such projects should equal or exceed the posted or regulatory speed in order to assure that drivers operating at the legal speed limit can do so without unwittingly exceeding the safe design speed of the facility.

    2. For all non-freeway 3R projects the design speed for specific elements may be determined and selected as described in Technical Advisory (TA) T 5040.28, "Developing Geometric Design Criteria and Processes for Non-freeway RRR Projects", dated October 17, 1988. The TA provides for selecting a design speed that equals or exceeds the posted or regulatory speed limit or as an alternate, the use of specific, measured 85th percentile speeds for design of individual or series of horizontal and vertical curves as recommended in the Transportation Research Board 3R study. The alternative procedure may be used whether or not the State has FHWA approved special 3R criteria.

    3. The intent of this policy is not to require speed limit posting or advisory speed signing to correspond to the actual design speed of the project or to an individual design element within a project. However, when the legal driving speed exceeds the design speed of a project element, the need for signs and markings should be based on recognized traffic engineering practice and accepted State policy, and be in accordance with the Manual on Uniform Traffic Control Devices.

  6. Bridges

    1. Bridge Widths. It is FHWA policy that the criteria contained in 23 CFR 625 apply in determining the width of all bridges to be constructed, reconstructed, or rehabilitated on the NHS. Exceptions may be provided on a project basis per 23 CFR 625 and within the delegated authority provided by FHWA Order M 1100.1. For rehabilitated bridges the provisions in 23 CFR 625 dealing with 3R projects may be applied. These provisions allow for flexibility in determining what geometric criteria are to be applied to 3R projects, including bridge widths other than full construction or reconstruction standards. Appropriate deck widths for rehabilitated bridges are to be determined on the basis that 3R projects must be designed and constructed in a manner that will enhance highway safety.

    2. Treatment of Existing Bridges on 3R/4R, Bridge Replacement, and Bridge Rehabilitation Projects

      • (1) On each project, a determination must be made as to whether an existing bridge should remain in place, be rehabilitated, or replaced. This decision should be based on an assessment of the bridge's structural and functional adequacy for the type and volume of projected traffic over its design life.

      • (2) The AASHTO design standards list minimum clear roadway widths for existing bridges to remain in place. Any exception to these standards should take into consideration the accident history, future traffic use, and general physical features of the bridge approach roadway as permitted in 23 CFR 625. When a decision is made to retain a bridge, the bridge rail should be evaluated to determine if it can adequately contain and redirect vehicles without snagging, penetrating, or vaulting. Consideration should be given to upgrading structurally inadequate or functionally obsolete bridge rail. The evaluation should be based upon criteria similar to that shown in NCHRP Report 239, "Multiple-Service-Level Highway Bridge Railing Selection Procedures." Guidance concerning width, rail and geometric criteria tradeoffs, and the effects on safety are contained in NCHRP's research Digest 98 and Report 203 both entitled, "Safety at Narrow Bridges." Appropriate traffic control devices should be installed where the clear roadway width is less than the approach roadway width.

      • (3) Rehabilitated bridges should be designed to at least the minimum AASHTO standards for new and reconstructed bridges. Exceptions to these standards may be approved based upon individual site evaluations; however, the rehabilitated bridges should, as a minimum, have at least an H15 load capacity and have an expected service life of 15 years or more. Bridges on the Interstate System, however, should have an HS-20 load capacity. Bridge rehabilitation projects must include correction of all major structural and safety defects. Substandard bridge rail should be upgraded to current standards and "safety" curbs which can cause vehicles to vault the rail should be eliminated. Exceptions may be considered on a case-by-case basis where safety can be adequately enhanced but cost-effective considerations prevent full widening or full upgrading of the bridge rail.

      • (4) Bridge replacement projects should meet the AASHTO standards for new bridges with very few exceptions. In the case of bridges on low volume roads and streets, exceptions may be appropriate if the existing road will not be upgraded in the foreseeable future (10 years or more).

      • (5) On all projects involving bridges, the approach guardrail should be evaluated and upgraded to current standards. Approach guardrail, if warranted, must be properly anchored to the bridge. The transition between the approach guardrail and the bridge rail should be smooth and of sufficient strength (i.e., reduced post spacing) to prevent snags and vehicle pocketing.

      • (6) Bridges which have been strengthened, replaced, or rehabilitated to eliminate deficiencies are to be reclassified as non-deficient in the bridge inventory. Those existing bridges for which FHWA has approved an exception to the AASHTO standards are also to be reclassified as non-deficient since it was determined that the bridge is adequate for the type and volume of projected traffic over its remaining design life. If exceptions were granted as a temporary measure because of a scheduled future replacement project, the bridge may remain classified as deficient.

    3. Bridge Rails. Bridge railing designs used for new and reconstructed bridges on the NHS shall have been successfully crash tested in accordance with NCHRP 350 criteria (or equivalents).

  7. Vertical Clearance on the Interstate System

    1. It must be emphasized that the integrity of the Interstate System for national defense purposes be maintained to meet AASHTO Policy as stated in A Policy on Design Standards - Interstate System, incorporated by reference in 23 CFR 625. On Interstate sections in rural areas, the clear height of structures shall be not less than 4.9 meters (16 feet) over the entire roadway width, including the usable width of shoulder. On Interstate sections in urban areas, the 4.9-meter (16-foot) clearance shall apply to a single routing. On other Interstate urban routes, the clear height of structures shall be not less than 4.3 meters (14 feet). Design exceptions must be approved whenever these criteria are not met.

    2. The FHWA has agreed that all exceptions to the 4.9-meter (16-foot) vertical clearance standard for the rural Interstate and the single routing in urban areas will be coordinated with the Military Traffic Management Command Transportation Engineering Agency (MTMCTEA) of the Department of Defense. This agreement applies whether it is a new construction project, a project that does not provide for correction of an existing substandard condition, or a project which creates a substandard condition at an existing structure. Furthermore, it applies to the full roadway width including shoulders for the through lanes, and to ramps and collector-distributor roadways in Interstate-to-Interstate interchanges.

    3. A number of toll roads have been incorporated into the Interstate System under the former provisions of Section 129(b) of Title 23, United States Code. While the FHWA does not have any particular "leverage" on the toll authorities to comply with Federal standards on non-federally funded projects, it is expected that the SHA's have established appropriate procedures to assure that proposed changes or alterations of the toll road will meet applicable policies established for the Interstate System. The working relationship should ensure the needs of the military are considered and that necessary coordination occurs.

    4. The approval action for Interstate design exceptions has been delegated to FHWA field offices and, in some cases, to the SHA. Whoever has responsibility for approving the design exception also is responsible for coordination with MTMCTEA. A request for coordination may be forwarded directly to the MTMCTEA at any time during project development but in all cases prior to taking any action on the design exception. It should include a time period of 10 working days (after receipt) for action on the request. The office initiating a request for coordination to the MTMCTEA can verify receipt of the request by telephone or fax. If the MTMCTEA does not respond within the time frame, it can be concluded that the MTMCTEA does not have any concerns with the proposed exception. If comments are forthcoming, the FHWA and/or SHA will consider mitigation to the extent feasible. A request for coordination should be addressed to:

      Military Traffic Management Command
      Transportation Engineering Agency (MTMCTEA)
      720 Thimble Shoals Boulevard, Suite 130
      Newport News, VA 23606-2574
      (Telephone: 757-599-1117, Fax: 757-599-1560)

  8. Design Exceptions
    1. General. The 23 CFR 625 provides that exceptions may be given on a project basis to designs which do not conform to the minimum criteria as set forth in the standards, policies, and standard specifications for: experimental features on projects and projects where conditions warrant that exceptions be made.

      • (1) Some project conditions that may warrant exceptions could be the extreme difficulty or high cost of obtaining right-of-way, cost of construction, mitigation of environmental impacts, or the preservation of historic or scenic values of the location. The careful application of the flexibility provided in the design standards and policies, appropriate use of design exceptions, and coordination with transportation enhancement activities can result in projects that provide safe and efficient transportation facilities and are sensitive and responsive to scenic and historic resources.

      • (2) Although all exceptions from accepted standards and policies should be justified and documented in some manner, the FHWA has established 13 controlling criteria requiring formal approval. These criteria are design speed, lane and shoulder width, bridge width, structural capacity, horizontal and vertical alignment, grade, stopping sight distance, cross slope, superelevation, and vertical and horizontal clearance (other than the "clear zone"). Design exceptions to these controlling criteria can, in the most part, be easily identified and defined. However, two items, horizontal clearance and design speed, warrant some further explanation and discussion.

        • (a) Horizontal Clearance: A recovery area clear of unyielding objects should be established for all projects. Criteria from the AASHTO Roadside Design Guide should be treated as guidance for setting individual project or statewide criteria or policies, not as a national standard requiring a design exception if not met.

        • (b) Design Speed: Design speed is a concept by which coordination of the various physical design elements is achieved. Design speed has a significant effect on the operation and safety of a highway because it is used to determine various individual design elements with specific dimensions such as stopping sight distance or horizontal curvature. Therefore, a "design speed exception" is necessarily an exception to individual physical design elements and accordingly must be justified on that basis.

      • (3) In a number of instances, a range of specific values of minimum, maximum, and desirable are contained in the AASHTO policies and guides. It is FHWA policy that the lowest or highest value of the range, whichever is appropriate, is to be considered as the minimum or maximum acceptable for design of NHS projects.

      • (4) For preventive maintenance projects, no exceptions are needed for the retention of existing substandard features. In effect, the State is maintaining the project as built, and as it was agreed upon in the project agreement. However, any new substandard features created, or existing ones made worse, must be covered by an exception since such actions in effect change the project as built.

    2. Evaluating Exceptions

      • (1) When evaluating a request for a design exception, consideration must be given to the effect of the variance from the design standard on the safety and operation of the facility and its compatibility with adjacent sections of roadway. Since safety enhancement is an essential element of any project design, exceptions should not be approved if the exception would result in degrading the relative safety of the roadway. Such factors as the functional classification of the road, the amount and character of the traffic, the type of project (i.e., new construction, reconstruction, or 3R), and the accident history should be considered in the evaluation. The cost of attaining full standards and any resultant impacts on scenic, historic or other environmental features, as well as whether any other future improvements are programmed should also be taken into consideration.

      • (2) Depending on the nature of the variance from the design standard, it may not be necessary to look at all of the above factors. However, before an exception is approved there should be compelling reasons why the adopted criteria should not be used. Three issues should be considered in any analysis: (a) what is the degree to which a standard is being reduced; (b) will the exception affect other standards; and (c) are there any additional features being introduced, e.g., signing or delineation, that would mitigate the deviation?

      • (3) One of the factors that has a significant influence on the appropriate design criteria is design speed. Since design speed affects curvature, sight distance, and other speed related features, care must be taken in the selection of the most appropriate value. Any design which uses a design speed below the posted or regulatory speed limit should not be approved.

      • (4) The amount and character of the traffic actually using the route, or that can legally use it (including trucks with grandfathered lengths), should be determined and used in the design exception process whether or not the route is on the National Network. It is recommended that permanent Interstate lane widths less than 11 feet not be approved except in only the most extreme and special cases. If Interstate lane widths less than 11 feet are used, they should be on a temporary basis only.

    3. Documentation. All exceptions to the design standards shall be identified and justified, taking into consideration the effect of any deviation from design standards on safety. The project files must include this information. Approved exceptions shall be identified either in project correspondence or on the project plans. Separate lists or a file of exceptions is recommended in order that the division office remains fully informed on the nature and extent of design exceptions being approved for given categories of projects.

    4. Review and Approval. If the FHWA is involved in reviewing and approving plans, specifications and estimates for any NHS project, then it also must review and approve design exceptions to standards applicable to that project. On those NHS projects on which the State has elected to apply one of the 23 U.S.C. 106(b) exemption provisions, which are administered under certification acceptance, or which are funded by other than Federal-aid funds, the State may approve design exceptions, but must evaluate and document the decision as if it were doing it for the FHWA. Design exceptions approved by the State for FHWA are still subject to FHWA oversight through periodic process reviews.

  9. Uniform Federal Accessibility Standards (23 CFR 625). The Uniform Accessibility Standards (UFAS) adopted by the General Services Administration (GSA) are to be used for design of all future buildings (and facilities) for which Federal and Federal-aid funds are used.

    1. The design of all new and altered rest area facilities must comply with the UFAS.

    2. The design of all new parking facilities must comply with the UFAS.

    3. The design of all pedestrian overpasses and underpasses must include ramps which do not exceed a 1:12 grade and platforms should be provided every 30 feet. Other features such as handrails and stairs (where stairs and ramps are used) should comply with UFAS. A 1979 agreement with the Architectural and Transportation Barriers Compliance Board (ATBCB) requires Washington Headquarters approval of all pedestrian overpasses and underpasses with grades that exceed a 1:12 slope or spacing of platforms of greater than 30 feet.

    4. The design of all facilities such as sidewalks and curb cuts not located on a building site should comply with the UFAS unless there is some compelling reason such as very steep terrain which does not permit compliance. Curb ramps, sidewalks, etc., on building sites must conform to the UFAS.

    5. A waiver may be obtained to the above accessibility design requirements on a case-by-case basis. Requests for waivers should be submitted together with a justification to the Washington Headquarters, HNG-14, for approval or submission to GSA.

  10. Prestressing Strand for Pretension Applications Development Length Revisited (23 CFR 625.4)

    1. As a result of evaluations and discussions, the criteria for strand development length in pretensioned applications is revised as follows:

      • (1) The use of 0.6-inch diameter strand in a pretensioned application at a 2-inch center-to-center of strand spacing is allowed;

      • (2) The use of 0.5-inch diameter strand in a pretensioned application at a 1.75-inch center-to-center of strand spacing is allowed;

      • (3) Development length for all strand shall be determined as 1.6 times AASHTO equation 9-42 (17th Edition); and

      • (4) Where strand is debonded (blanketed) at the end of a member, and tension at service load is allowed in the precompressed tensile zone, the development length shall be determined as 2.0 times AASHTO equation 9-42 (17th Edition), as currently required by AASHTO article 9.28.1.

    2. Exceptions to the above criteria are as follows:

      • (1) Development length for prestressed piling subjected to flexural loading shall be determined as indicated above. Development length for embedded piling not subjected to flexural loading shall be determined as per AASHTO equation 9-42 (17th Edition), and the use of 0.6-inch diameter strand will be allowed.

      • (2) Development length for pretensioned precast sub-deck panels or precast pretensioned voided deck plank, shall be determined as outlined above, or alternatively, by utilizing AASHTO equation 9-42 for development length and designing and tensioning on the basis of a guaranteed ultimate tensile strength (GUTS) of 250 ksi and release of prestressed at 70 percent of GUTS regardless of the type of strand used (i.e., 250 or 270 ksi strand).

    3. The above criteria and exceptions are an interim measure, until such time as the research indicates otherwise and AASHTO adopts the results.

  11. Epoxy Coated Reinforcing Steel for Bridge Decks (23 CFR 625). As the result of recent laboratory and field studies, questions regarding the long-term performance and overall effectiveness of epoxy coated reinforcement (ECR) have been raised. The current policy of the FHWA is to continue to support the use of ECR as an alternative cost-effective means of combatting corrosion in bridge decks. However, the FHWA strongly recommends that the States:

    1. Evaluate existing specifications and strengthen provisions where appropriate. In particular, minimum film thickness, holiday limits and testing, allowable bare areas and strong positive provisions for detecting and patching bare areas found at job-sites should be included.

    2. Inspections of fabricating plants supplying ECR for State projects should be made. While the Concrete Reinforcing Steel Institute Certification Program is a significant step in the right direction, the States should not relinquish vigilance over coating operations and overall production of ECR.

    3. Thoroughly inspect the coated steel delivered to the job-site and after installation in the forms to ensure that or is not damaged, and that when there is damage, it has been properly patched.

    4. See that bars are stored properly, both at the coating plant and on the job-site. For example, it is known that the epoxy coating can suffer from ultraviolet light degradation if left exposed outdoors too long. (Some experts recommend limiting exposure to 3 months or less.) Extended outdoor storage of coated bars, either at the coating plant or the job-site, or the combination of the two, should be avoided. If the stored bars are subject to exposure to aggressive environments, e.g., salt laden air, the bars should be stored off of the ground either indoors or outdoors. If stored outdoors, the bars should be covered for protection against the elements and in such manner that condensation does not form on the bars.

    5. Provide multiple corrosion protective systems in marine or harsh environments for bridge decks on critical high-volume traffic structures. In addition, multiple corrosion protective systems should also be used for other structural components that are subjected to marine or harsh, aggressive environments.

    6. Use durable quality concrete and provide adequate cover over the reinforcing steel. These points cannot be emphasized enough for effective prevention of reinforcing steel corrosion.

    7. Evaluate the corrosion performance and adhesion characteristics of ECR in existing bridge decks. The individual States may use SPR or other research funds to evaluate the integrity of the epoxy coating in existing decks after several years of service. These studies might also assist in determining if specification ECR is being placed into decks following normal construction practices.

  12. Construction and Contract Management of Major and Unusual Structures (23 CFR 625). Previous information issued on this subject is clarified and amplified by this supplement as follows:

    1. It is the sole responsibility of the contractor to construct and/or erect the structure in a safe and prudent manner and the contract documents should so indicate.

    2. Current state-of-the-art type structures, more often than not, require that the designer assume a method of construction and/or erection (balanced cantilever, span-by-span incremental launching, strand tendons versus bar tendons, erection loads and/or equipment, etc.) in order to design the structure. Assumed construction loads and erection method loads should be indicated in the general notes of the drawings and clearly state that they were assumed for design purposes only.

    3. In many instances the designer will provide schematic erection sequence drawings based upon the assumed method of construction/erection. These drawings should be placed in a clearly defined appendix to the contract drawings and clearly indicate that they are provided for information only and the if the contractor elects to use the methodology depicted, it is the contractor's responsibility to determine the appropriateness and adequacy of the method depicted.

    4. Contractor options and/or limitations to options should be clearly delineated in the contract documents.

    5. The contractor should be required to submit, for review by the Engineer, his or her construction/erection method, erection equipment drawings indicating loads imposed on the structure during all phases of erection falsework design and all supporting calculations as may be required to indicate the stress level resulting therefrom. All such documents are to be prepared and stamped by a registered Professional Engineer familiar with the particular methods and/or procedures being proposed.

    6. It should be clearly stated in the contract documents that the Engineer's review does not in any way absolve the Contractor from responsibility for the structural adequacy of the construction /erection methods and/or the erection equipment. The Engineer's review is only to:

      • (1) determine that appropriate design specifications have been complied with; and

      • (2) that any temporary stresses imposed upon the structure or permanent (locked-in) stresses in the completed structure, resulting from the construction/erection method or construction equipment, are within allowable limits.

    7. Any modification to the structure from the contract documents resulting from construction/erection loads imposed on the structure in excess of that assumed in design is to be at the contractor's expense and be approved by the Engineer.

    8. The above notwithstanding, where there is a risk to the general public from construction/erection activities and/or falsework over or adjacent to travelled roadways, navigation or recreational waterways, existing operational, commercial or industrial facilities, etc., it should be the responsibility of the State or its consultant to do a sufficiently detailed in-depth review of the contractor's proposed methods and/or procedures to establish adequacy and safety.

  13. TIED ARCH BRIDGES (23 CFR 625). Because tied arch bridges have only two main supporting members, there is little redundancy with regard to catastrophic failure. For this reason, any future preliminary plans for this type of structure should be submitted to the Washington Headquarters office at an early date for review and possible suggested use of an alternate structure type.

  14. MARYLAND ROUTE 198 BRIDGE FALSEWORK FAILURE - BOARD OF REVIEW - FINAL REPORT (23 CFR 625). As the result of the August 31, 1989, falsework related bridge collapse of the Route 198 bridge over the Baltimore-Washington Parkway in Maryland, the Federal Highway Administration established a Board of Review to evaluate the failure and make recommendations to avoid future occurrences. The major recommendations of the Board of Review which were strongly endorsed and should be implemented include:

    1. Falsework specifications should be revised to better define the responsibilities of material suppliers, contractors, and engineers. To minimize the possibility that this type of situation occurs in the future, highway agencies should review their falsework specification and construction procedures and strengthen them, where needed.

    2. It is very important that every bridge on a project receive a separate falsework design analysis. On the subject project the same design analysis was used for two separate bridges even though the beam spacing differed slightly between the two. As a result, the falsework support beams were not directly under the webs of the second bridge which subsequently failed during concrete placement.

    3. In the event that falsework is moved from one bridge to another, the falsework should be thoroughly inspected for structural damage and plumbness to ensure that all members are in place and properly aligned and connected.

    4. Manufactured products that require certification by the manufacturer have been a problem on some highway construction projects. Contractors and engineers generally accept a certificate for specification compliance. In essence, manufactured shoring tower assemblies are considered to be certified through the contractor submitting catalog data to the engineer. This catalog information shows the shoring tower configurations, screw jack criteria, and other design information that is used in the design of the overall falsework system. For the subject bridge, the contractor did not construct the approved and certified shoring towers, Instead, the shoring tower assemblies that were furnished contained undersized jacks and consisted of components from several other manufacturers. The Board recommends that highway agencies should require:

      • (1) All falsework design submittals be formally signed and sealed by the contractor's registered Professional Engineer.

      • (2) The contractor's registered Professional Engineer certify that the falsework system has been assembled according to the approved falsework drawings, prior to placing loads on the falsework.

    5. Each falsework system should be designed to handle all vertical and horizontal loading and to contain enough redundancy to prevent a failure in the entire system. Vertical loading and differential settlement forces, and horizontal lateral and longitudinal forces should be taken into account. Unbalanced temporary loading, caused by the placement sequence, should also be considered.

    6. When falsework installations are to be placed adjacent to an open public road, special design considerations and protection should be taken to ensure that the falsework system is not disturbed by errant highway vehicles or from vibration forces caused by passing vehicles.

    7. This post-failure investigation points out the importance of the highway agency moving quickly to preserve and document the in-place failure and to assign investigation responsibilities to qualified impartial parties.

  15. Metal Stay-in-Place Bridge Deck Forms (23 CFR 625)

    1. Virtually all States allow the use of metal stay-in-place bridge deck forms. The introduction of longer span forms, up to 4.8 meters (15 feet), suggest that a review of existing specifications and requirements is appropriate to insure that cost-effective designs are not being compromised.

    2. To meet AASHTO Specifications, it is necessary to ensure that adequate cover is provided and that all dead loads are accounted for in the design. The limits of deflection suggested by at least one manufacturer (L/240 not to exceed 3/4") has been used successfully, with FHWA approval, in Pennsylvania. For design purposes, this appears to be a practical limit.

    3. Designs should incorporate an allowance for the weight of the form and additional concrete (15psf), with the provision that if it is exceeded, the contractor is responsible to show that the effects on the rest or the bridge are acceptable, or, to provide additional strengthening if necessary, at no expense to the owner.

  16. Guides and References

    The following are citations to publications that are primarily informational or guidance in nature and serve to assist the public in knowing those materials that are considered by the Federal Highway Administration (FHWA) to provide valuable information in attaining good design. The number in brackets following each citation indicates the location of the document as listed in the Appendix.

    1. Roadways and appurtenances

      • (1) An Informational Guide for Roadway Lighting, American Association of State Highway and Transportation Officials (AASHTO) 1985. [2]

      • (2) Highway Safety Design and Operations Guide, AASHTO 1997. [2]

      • (3) Roadside Design Guide, AASHTO 2002. [2]

      • (4) An Informational Guide on Fencing Controlled Access Highways, AASHTO 1990. [2]

      • (5) Highway Capacity Manual, Transportation Research Board (TRB), 2000. [4]

      • (6) Pavement Management Guide, AASHTO 2001. [2]

      • (7) Guidelines for Geometric Design of Very Low-Volume Local Roads (ADT<400), AASHTO 2001. [2]

      • (8) Skid Accident Reduction Program, T 5040.17, FHWA December 23, 1980. [1]

      • (9) Guidelines for Skid Resistant Pavement Design, AASHTO 1976. [2]

      • (10) Special Report 214, Designing Safer Roads, Practices for Resurfacing, Restoration, and Rehabilitation, TRB 1987. [4]

      • (11) AASHTO Guide for Design of Pavement Structures, AASHTO 1993. [2]

      • (12) National Cooperative Highway Research Program Report 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features, TRB 1993. [4]

      • (13) Guide for the Design of High Occupancy Vehicle Facilities, AASHTO 1992. [2]

      • (14) Roundabouts: An Informational Guide, Publication No. FHWA-RD-00-067, FHWA 2000. [1]

      • (15) A Guide for Transportation Landscape and Environmental Design, AASHTO 1991. [2]

    2. Bridges and structures

      • (1) Guidelines for Bridge Management Systems, AASHTO 1993. [2]

      • (2) Manual for Condition Evaluation of Bridges, AASHTO 2000. [2]

      • (3) A Guide for Protective Screening of Overpass Structures, AASHTO 1990. [2]

      • (4) Guide Specifications for Fracture Critical Non-Redundant Steel Bridge Members, AASHTO 1978, and amending Interim Specifications - Bridges, AASHTO 1981 through 1990. [2]

      • (5) Guide Specifications for Horizontally Curved Highway Bridges, AASHTO 1980, and amending Interim Specifications - Bridges, AASHTO 1981 through 1993. [2]

      • (6) Guide Specifications for Aluminum Highway Bridges, AASHTO 1991. [2]

      • (7) Guide Specifications for Seismic Isolation Design, AASHTO 1999. [2]

      • (8) Guide Specifications for the Design of Stress- Laminated Wood Decks, AASHTO 1991. [2]

      • (9) Guide Specifications and Commentary for Vessel Collision of Highway Bridges, AASHTO 1991. [2]

      • (10) Guide Specifications for Fatigue Evaluation of Existing Steel Bridges, AASHTO 1990, and Interim Specifications - Bridges, AASHTO 1993. [2]

      • (11) AASHTO Guide Specifications - Thermal Effects in Concrete Bridge Structures, AASHTO 1989. [2]

      • (12) Guide Specifications for Fatigue Design of Steel Bridges, AASHTO 1989, and Interim Specifications - Bridges, AASHTO 1993. [2]

      • (13) Guide Specifications for Strength Evaluation of Existing Steel and Concrete Bridges, AASHTO 1989. [2]

      • (14) Guide Specifications for Design and Construction of Segmental Concrete Bridges, AASHTO 1989, and Interim Specifications -Bridges, AASHTO 1994. [2]

      • (15) Guide Specifications for Structural Design of Sound Barriers, AASHTO 1989, and Interim Specifications - Bridges, AASHTO 1992. [2]

      • (16) Guide Specifications for Bridge Railings, AASHTO 1989, and Interim Specifications - Bridges, AASHTO 1990 through 1992. [2]

      • (17) Guide Specifications for Alternate Load Factor Design Procedures for Steel Beam Bridges Using Braced Compact Sections, AASHTO 1991, and Interim Specifications - Bridges, AASHTO 1994. [2]

      • (18) Guide Specifications for Strength Design of Truss Bridges (Load Factor Design), AASHTO 1986. [2]

      • (19) Guide Specifications for Distribution of Loads for Highway Bridges, AASHTO 1994. [2]

      • (20) Recommendations for Stay Cable Design, Testing and Installation, Post-Tensioning Institute 2000. [5]

      • (21) Model Drainage Manual, AASHTO 1991. [2]

      • (22) Highway Drainage Guidelines, Volumes I through X, AASHTO 1992, and Volume XI, AASHTO 1994. [2]

      • (23) Manual on Subsurface Investigations, AASHTO 1988. [2]

      • (24) Soils and Foundations Workshop Manual, FHWA 1994. [1]

    3. Other

      • (1) Transportation Glossary, AASHTO 1983. [2]

      • (2) A Guide for Erecting Mailboxes on Highways, AASHTO 1994. [2]

      • (3) Guide for Development of Rest Areas on Major Arterials and Freeways, Third Edition, AASHTO 2001. [2]

      • (4) Guide for the Development of Bicycle Facilities, AASHTO 1999. [2]

      • (5) Guide Specifications for Highway Construction, AASHTO 1993. [2]

      • (6) Guide for the Design of Park-and-Ride Facilities, AASHTO 1992. [2]

      • (7) Guide to Wetland Mitigation Issues for Transportation Designers, AASHTO 1996. [2]

      • (8) Building a True Community, U.S. Access Board 2001. [6]

      • (9) Designing Sidewalks and Trails for Access, Publication No. FHWA-EP-01-027, FHWA 2001. [1]

      • (10) Flexibility in Highway Design, Publication No. FHWA-PD-97-062, FHWA 1997. [1]

      • (11) A Guide to Best Practices for Achieving Context Sensitive Solutions, National Cooperative Highway Research Program (NCHRP) Report 480, TRB 2002. [4]

Appendix A - Document Availability

These documents may be reviewed at the following locations:

  1. Department of Transportation Library, 400 7th Street, SW, Room 2200, Washington, DC 20590.

  2. American Association of State Highway and Transportation Officials, Suite 249, 444 North Capitol Street, NW, Washington, DC 20001.

  3. American Welding Society, 2501 Northwest 7th Street, Miami, FL 33125.

  4. Transportation Research Board, 2101 Constitution Avenue, NW, Washington, DC 20418.

  5. Post-Tensioning Institute, 1717 W. Northern Avenue, Suite 114, Phoenix, Arizona 85021.

  6. U.S. Access Board, 1331 F Street, NW, Suite 1000, Washington, DC 20004-1111.

Additional Information

Updated: 06/27/2017
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