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FHWA Home / Safety / Roadway Departure / Safety Eligibility Letter

Safety Eligibility Letter CC-101

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U.S. Department of Transportation
Federal Highway Administration

1200 New Jersey Ave. S.E.
Washington, D.C. 20590

June 3, 2008

In Reply Refer To: HSSD/CC-101

Hayes E. Ross, Jr., P.E., Ph.D.
Professor Emeritus
Civil Engineering Department
Texas Transportation Institute
3135 TAMU
College Station, TX 77843-3135

Dear Dr. Ross:

This letter is in response to your request for Federal Highway Administration (FHWA) acceptance of a roadside safety device for use on the National Highway System (NHS).

Name of device: 27-inch high Steel Post Slotted Rail Terminal (SRT-27SP)
Type of device: W-Beam Guardrail Terminal
Test Level: TL-3
Testing conducted by: Texas Transportation Institute
Date of request: November 29, 2007
Date of follow-up: March 26, 2008

You requested that we find this device acceptable for use on the NHS under the provisions of National Cooperative Highway Research Program (NCHRP) Report 350 “Recommended Procedures for the Safety Performance Evaluation of Highway Features.”

Requirements
Roadside safety devices should meet the guidelines contained in the NCHRP Report 350, "Recommended Procedures for the Safety Performance Evaluation of Highway Features". FHWA memorandum “Action: Identifying Acceptable Highway Safety Features” of July 25, 1997 provides further guidance on crash testing requirements of longitudinal barriers.

Description
The Slotted Rail Terminal was first covered by FHWA Acceptance Letter CC-31 dated December 4, 1999 and followed by CC-31A, CC-51, and CC-51A. Variations include the original wood post design at 27 inches, a design substituting two steel Hinged Breakaway Posts for two of the system’s wood posts, and an all-steel design without blockouts but with the rail mounted at 31 inches. Your present request is for an all-steel post version with the rail mounted at 27 inches.

The SRT-27SP is:

  1. An all steel terminal (except for the offset blocks).
  2. Standard 6x8 inch routed wood terminal blockout or other FHWA-Accepted alternative blockouts used at posts 3 through 6.
  3. Steel Yielding Terminal Posts (SYTP) are used at posts 2 through 6.
  4. A steel Cable Release Post is used at post 1.
  5. The rail is detached from the support posts 2 through 5.
  6. A shelf angle at post 2 provides rail support.
  7. The terminal is 37.5 feet long with a straight flare and a 4 foot end offset.

Crash Testing
No additional testing was conducted on the SRT-27SP. Rather you provided a detailed comparison of test results from tests on earlier versions of the SRT and evaluated the need to conduct a similar test on the SRT-27SP. The following barrier terminal tests were reviewed:

On March 26, 2008, you spoke with Mr. Nicholas Artimovich of my staff and explained the rationale behind each required test and the prior testing that satisfies NCHRP Report 350 requirements.

Findings
We concur with your analysis of prior testing and agree that additional tests are not necessary to qualify the SRT-27SP. Therefore the subject w-beam guardrail terminal is acceptable for use on the National Highway System when permitted by a highway agency.

Please note the following standard provisions that apply to FHWA letters of acceptance:

Sincerely yours,

David A. Nicol, P.E.
Director, Office of Safety Design
Office of Safety

Enclosures

Page last modified on January 17, 2013.
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Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000