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                Safety Eligibility Letter B-141C
  
  **Hardware Type:**
            Longitudinal Barriers and Bridge Rails
                          **Code:**
            B-141C
                          **Date:**
            11/14/2008
                          **Testing Criteria:**
            NCHRP 350
                          **Manufacturer:**
            Trinity Industries
                          **Device Description:**
            CASS on 4:1 slope to 350 REVISED
                          **View PDF:**
            b141c.pdf (50.31 KB)
    
    Safety Eligibility Letter B-141C
			
			
			 
			**Download Version**PDF [50.3 KB]
			
			DOT logoU.S. Department of Transportation**Federal Highway Administration**
			1200 New Jersey Ave. S.E.Washington, D.C. 20590
			November 14, 2008
			In Reply Refer To: HSSD/B-141C **(REVISED)**
			
			Mr. Brian Smith
				Trinity Highway  Products, LLC 
				P.O. Box 568887
				Dallas, TX 75356-8887
				
			Dear Mr. Smith:
			This letter is in response to your request for Federal  Highway Administration (FHWA) acceptance of a roadside safety system for use on  the National Highway System (NHS).
			Name of system:  CASS cable barrier system on a 4:1 slope
				Type of system:  Three cable median barrier
				Test Level: National Cooperative  Highway Research Program (NCHRP) Report 350
				Testing conducted by: Texas  Transportation Institute (TTI)
				Dates of  request: November 28, 2007 and February 5, 2008,
				Date of  completed package: June 22, 2008
				Letter revised:  October, 2008You requested that we find this system acceptable for use on  the NHS under the provisions of the NCHRP Report 350 “Recommended Procedures  for the Safety Performance Evaluation of Highway Features.”
			**Introduction**The FHWA guidance on crash testing of roadside safety  hardware is contained in a memorandum dated July 25, 1997, titled “INFORMATION:  Identifying Acceptable Highway Safety Features.”
			The       CASS 4:1 is a tensioned, three-cable barrier system that was tested with       standard (non-prestretched) cables.       The middle and top cables are positioned within a wave-shaped slot in the web of S100 x 11.5 (S4 x  7.7#) structural I-beam posts. The  bottom cable is supported on the median-side flange of the I-beam post by an 8  mm (5/16 inch) hook  bolt with the open end down. The  proprietary S100 x 11.5 (S4 x 7.7#) posts have weakening holes at the ground  line and were installed in steel tube sleeves set in 305 mm (12 inch) diameter x 762 mm (30 inch) deep  concrete footings. Post spacing was 6.1  m (20 feet) for the first three tests and 2.03 m (6  feet 8 inches) for the fourth test. The  cables within the wave-shaped slot are separated by plastic spacers. A stainless steel strap is mounted on the  outside of the post above the top cable.The 19 mm (3/4-inch) diameter standard cables were set at  heights of 445 mm, 745 mm, and 1060 mm (17.5, 29.3, and 41.7 inches) above the  ground surface, measured to the center of each cable. Tension of the cables was set at 24.9 kN  (5600 pounds force) for the tests.
			**Testing**Three tests were conducted on the CASS 4:1 system with 6.1m (20 feet 0 inch) post spacing installed in  a 9.1 m (30 foot) wide depressed median with 1V:4H side slopes. A fourth test was conducted on the CASS 4:1  system with 2.03 m (6 feet 8 inch) post spacing. The barrier installations and tests  intended to show that the system would perform properly when located 1.22 m (4  feet) from the hinge point and 3.5 m (11 feet) from the ditch invert. The test data summary sheets are attached,  and the tests are briefly described as follows:
			The NCHRP Report 350 Test 3-11 (modified) – 2270P  (MASH-08 pickup truck) at 100 km/hr with a 25 degree impact angle. The barrier was installed 1.22 m (4 feet)  from the break point.
				The NCHRP Report 350 Test 3-10 – 820C at 100 km/hr with a  20 degree impact angle with the barrier installed 1.22 m (4 feet) from the  break point.
				The NCHRP Report 350 Test 3-10 – 820C at 100 km/hr with a  20 degree impact angle with the barrier installed on the median backslope 3.35  m (11 feet) from the median bottom. The  test vehicle traveled across the median bottom and traveled up the backslope  before impacting the barrier.
				The NCHRP Report 350 Test 3-11 (modified) – 2270P  (MASH-08 pickup truck) at 100 km/hr with a 25 degree impact angle. The barrier was installed 1.22 m (4 feet)  from the break point.  Post spacing was 2.03 m (6 foot 8 inch) post spacing.Each 100.6 m (330 foot long) test installation was anchored  by TTI Breakaway Cable Anchor Terminals.  Dynamic deflection in Test 3-11 (modified) with  6.1 m (20 foot) spacing was 2.85 m (9.35 feet.)  Dynamic deflection in Test 3-11 (modified) with 2.03 m (6 foot 8 inch)  spacing was 2.19 m (7.19 feet.)
			You initially requested the FHWA Acceptance under the MASH-08  as you used the appropriate quad-cab pickup truck. Subsequently you agreed with the FHWA that the  300-foot length of the test article was inadequate under the MASH-08  guidelines, but that the 2270P vehicle would be considered acceptable for  judging performance under the NCHRP Report 350 in this matrix.
			**Findings**The occupant risk values and vehicle trajectories in all  four tests met the appropriate evaluation criteria. None of the tests showed potential for vehicle override, penetration, or rollover. Therefore, the system placed on a  1V:4H or flatter median slope described above and detailed in the enclosed  drawings is acceptable for use on the NHS under the range of conditions tested,  when the barrier’s use is approved by a highway agency under both the  NCHRP Report 350. Although testing was  conducted on standard cables, we concur with your additional request that the  system be found acceptable with pre-stretched cables.
			Although the barrier  performed well under ideal test impact conditions when originally crash tested,  the likelihood of passenger car underrides of **any cable system**may  increase as the post spacing increases, particularly when the barrier is  installed on non-level or slightly irregular terrain and the cables are not  restrained from lifting at each post.  Consequently, some transportation agencies have limited post spacing to  approximately 6 m (20 feet) for cable barriers.  The dynamic deflection of the barrier is likely to increase when it is  installed along the convex sides of horizontal curves, and when distances between  anchorages exceed the 350 foot test length.
			Sincerely yours,
						George E. Rice, Jr.
						*for*
								David A. NicolDirector, Office of Safety DesignOffice of Safety U.S. DEPARTMENT OF TRANSPORTATION

**Federal Highway Administration**

1200 NEW JERSEY AVENUE, SE

WASHINGTON, DC 20590

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