Section 2: FHWA Policy on Bridge Railing
Anchor: #i1000605Overview
Since September 1, 1986, the Federal Highway Administration (FHWA) has required highway bridges on the National Highway System (NHS) and the Interstate Highway System to have crash-tested railing. Current policy is stated in the following documents:
- Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA). http://www.fhwa.dot.gov/legsregs/legislat.html Requires that measures to enhance the crash worthiness of roadside features accommodate vans, minivans, pickup trucks, and 4-wheel drive vehicles, as well as cars.
- National Cooperative Highway Research Program (NCHRP) Report 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features. http://safety.fhwa.dot.gov/programs/roadside _hardware.htm
-
Provides guidance for testing highway features to assess safety performance of those features, replacing guidance defined in NCHRP Report 230. Guidance includes definitions of crash-test levels with specified vehicle, speed, and impact angle for each level.
- “Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation’s Bridges.” Report No. FHWA-PD-96-001, p. 69.
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Clarifies that “safety feature replacement or upgrading (for example, bridge rail...)” is a type of work eligible for funding under any of the Federal aid categories but not considered as reconstruction and, therefore, not activating the FHWA’s “Ten Year Rule” (see linked memorandum), which disqualifies a bridge for additional federal aid Highway Bridge Program funds for a period of ten years after any federal funds have been used on a new bridge, reconstructed bridge, or major bridge rehabilitation.
- May 30, 1997, memorandum from Dwight Horne on the subject
of “Crash Testing of Bridge Railings.”
http://safety.fhwa.dot.gov/fourthlevel/hardware/pdf/bridge.pdf
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Identifies 68 crash-tested bridge rails, consolidating earlier listings and establishing tentative equivalency ratings that relate previous testing to NCHRP Report 350 test levels. Ten of the 68 crash-tested rails were developed and tested in Texas.
- July 25, 1997, memorandum from Donald Steinke on the subject of “Identifying Acceptable Highway Safety Features.”
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Clarifies and summarizes policies on bridge railing, points to authorities for requiring testing of bridge railing, and identifies methods for submitting new rails for testing. This document also identifies exceptions, one of which is the replacement or retrofitting of existing bridge railing unless improvements are being made on a stretch of highway that includes a bridge with obsolete railing.
- August 28, 1998, memorandum from Henry Rentz on the subject of “National Cooperative Highway Research Program (NCHRP) Report 350 Hardware Compliance Dates” and the attachment to the memorandum.
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Extends implementation dates and adds caveats for use of safety hardware in new installations and 3R projects. Explicitly assigns responsibility to transportation agencies for defining “...when extensions, relocation, adjustments or major repairs to a feature constitute a new installation” and whether “...features that meet the acceptance requirements recommended in NCHRP Report 230...may remain in place.”
- May 16, 2000, memorandum from Frederick Wright on the subject of “Bridge Rail Analysis.”
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http://safety.fhwa.dot.gov/fourthlevel/hardware/ pdf/bridgerail_analysis_may16.pdf
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Allows responsible transportation agencies to request FHWA acceptance of a specific bridge railing type that has not been crash tested based on analysis showing its similarity to a design that has been crash-tested and found compliant with NCHRP-350 requirements.
On its web site, FHWA provides current information on three general categories of roadside hardware that are tested and evaluated using NCHRP Report 350 criteria; one of those categories is Bridge Railing: http://safety.fhwa.dot.gov/fourthlevel/hardware/bridgerailings.htm
In summary, FHWA policy is that all new or replacement railing on National Highway System or Interstate Highway System bridges must meet Test Level 3 (TL-3) crash-test criteria at a minimum. However, responsible transportation agencies have limited latitude to define when existing railing that complies with requirements of NCHRP Report 230 must be replaced.
Anchor: #i1000694Required Crash Tests
For evaluating bridge railing, the NCHRP Report 350 defines two occupant-hazard tests and six strength tests at each crash-test level, as follows.
|
Test |
Test Level (TL) |
Vehicle |
Speed |
Angle of Impact |
|---|---|---|---|---|
|
Occupant Hazard |
TL-1 |
1973-lb. small car |
31 mph |
20 degrees |
|
|
TL-1 |
4409-lb. pickup truck |
31 mph |
25 degrees |
|
|
TL-2 |
1973-lb. small car |
43 mph |
20 degrees |
|
|
TL-2 |
4409-lb. pickup truck |
43 mph |
25 degrees |
|
|
TL-3 through TL-6 |
1973-lb. small car |
62 mph |
20 degrees |
|
|
TL-3 through TL-6 |
4409-lb. pickup truck |
62 mph |
25 degrees |
|
Strength of Railing |
TL-1 |
4409-lb. pickup truck |
31 mph |
25 degrees |
|
|
TL-2 |
4409-lb. pickup truck |
43 mph |
25 degrees |
|
|
TL-3 |
4409-lb. pickup truck |
62 mph |
25 degrees |
|
|
TL-4 |
17,637-lb. single-unit truck or school bus |
50 mph |
15 degrees |
|
|
TL-5 |
79,366-lb. truck with van trailer |
50 mph |
15 degrees |
|
|
TL-6 |
79,366-lb. truck with tank trailer |
50 mph |
15 degrees |
|
NOTE: Occupant-hazard and strength tests using the pickup are the same for TL-1 through TL-3. |
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