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FHWA Home / Safety / Roadway Departure / Safety Eligibility Letter

Safety Eligibility Letter B-141F

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U.S. Department of Transportation
Federal Highway Administration

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

October 1, 2010

In Reply Refer To:
HSSD/B-141F

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 the Federal Highway Administration (FHWA) acceptance of modifications to your CASS cable barrier safety system for use on the National Highway System (NHS).

Name of system: Trinity's Cable Safety System (CASS S3 4:1)
Type of system: Four cable median and roadside barrier system
Test Level: NCHRP Report 350:
Test Level 3 on 1:4 slopes or flatter
Test Level 4 on 1:6 slopes or flatter
Testing conducted by: Texas Transportation Institute
Date of request: March 5, 2010

You requested that we find this system acceptable for use on the NHS under the provisions of National Cooperative Highway Research Program (NCHRP) Report 350 "Recommended "

Requirements
Roadside safety systems should meet the guidelines contained in the NCHRP Report 350. The FHWA memorandum "Identifying Acceptable Highway Safety Features" of July 25, 1997, provides further guidance on crash testing requirements of longitudinal barriers.

Description
The CASS S3 4:1 is a tensioned, four-cable barrier system that was tested with standard (non-prestretched) cables. The top two cables are positioned within a wave-shaped slot in the web of S75 x 8 (S3 x 5.7 in English units) structural I-beam posts. The bottom two cables are supported on flanges of the I-beam post by an 8-mm (5/16-inch) hook bolt with the open end down, with the lowest cable located on the median-side flange and the next lowest cable located on the traffic-side flange.

The proprietary S75 × 8 (S3 × 5.7) posts were installed in steel tube sleeves set in 305-mm (12-inch) diameter x 762-mm (30-inch) deep concrete footings. The cables within the wave-shaped slot are separated by a plastic spacer. A stainless steel strap is mounted on the outside of the post above the top cable.

The 3/4-inch diameter standard (non-pre-stretched) cables were set at heights of 450mm, 755mm, 960 and 1070mm (17.75, 29.75, 37.875, and 42.125 inches) above the ground surface, measured to the center of each cable. Tension of the cables was set at 24.9 kN (5,600 pounds
force) for the tests.

The 104.7-m (343-foot, 6-inch) test installations were anchored by Texas Transportation Institute (TTI) Breakaway Cable Anchor Terminals which were accepted by the FHWA on August 29, 2002.

Four tests were conducted with the CASS S3 4:1 system installed in a 9.1m (30 foot 0 inch) wide depressed median with 1V: 4H side slopes, and one test with the CASS S3 4:1 system installed on level terrain:

  1. The NCHRP Report 350 Test 3-11 (modified) - 2270P at 102.6 km/hour (63.7 mph) with a 25.4 degree impact angle. The test article was the CASS S3 4:1 with 3.2-m (10-foot, 6-inch) post spacing installed on the foreslope of a 9.1-m (30-foot, 0-inch) wide depressed median with 1V: 4H side slopes at 1.22m (4 foot, 0 inch) from the break point.

    The CASS S3 4:1 on 1V:4H foreslope contained and redirected the 2270P vehicle. The vehicle did not penetrate, under ride, or override the installation. Dynamic deflection in Test 3-11 (modified) with 3.2-m (10-foot, 6-inch) post spacing was reported by TTI to be 2.16m (7.1 feet).

  2. The NCHRP Report 350 Test 3-10 - 820C at 102.1 km/hour (63.4 mph) with a 20.8 degree impact angle. The test article was the CASS S3 4:1 with 6.1-m (20-foot, 0-inch) post spacing installed on the backslope of the 9.1-m (30-foot, 0-inch) wide depressed median at 3.35m (11 feet 0 inch) from the median bottom. The test vehicle crossed the median bottom and traveled up the backslope before impacting CASS S3 4:1.

    The CASS S3 4:1 on 1V:4H backslope contained the 820C vehicle, which then sideslipped along the system until loss of contact. The vehicle did not penetrate, under ride, or override the installation. Dynamic deflection in Test 3-10 (backslope) with 6.1-m (20-foot, 0-inch) post spacing was reported by TTI to be 1.34m (4.4 feet).

  3. The NCHRP Report 350 Test 3-10 - 820C at 97.3 km/hour (60.4 mph) with a 19.5 degree impact angle. The test article was the CASS S3 4:1 with 3.2-m (10-foot, 6-inch) post spacing installed on the foreslope of a 99.1-m (30-foot, 0-inch) wide depressed median with 1V: 4H side slopes at 1.22m (4 foot, 0 inch) from the break point.

    The CASS S3 4:1 on 1V:4H foreslope contained and redirected the 820C vehicle. The vehicle did not penetrate, under ride, or override the installation. Dynamic deflection in Test 3-10 with 3.2-m (10-foot, 6-inch) post spacing was reported by TTI to be 1.04m (3.4 feet).

  4. The NCHRP Report 350 Test 3-11 (modified) - 2270P at 102.4 km/hour (63.6 mph) with a 25.4 degree impact angle. The test article was the CASS S3 4:1 with 6.4-m (21-foot, 0-inch) post spacing installed on the foreslope of a 9.1-m (30-foot, 0-inch) wide depressed median with 1V: 4H side slopes at 1.22m (4 foot, 0 inch) from the break point.

    The CASS S3 4:1 on 1V:4H foreslope contained and redirected the 2270P vehicle. The vehicle did not penetrate, under ride, or override the installation. Dynamic deflection in Test 3-11 (modified) with 6.4-m (21-foot, 0-inch) post spacing was reported by TTI to be 2.59m (8.5 feet).

  5. The NCHRP Report 350 Test 4-12 - 8000S at 79.9 km/hour (49.6 mph) with a 13.6 degree impact angle. The test article was the CASS S3 4:1 with 3.2-m (10-foot, 6-inch) post spacing installed on level terrain.

    The CASS S3 4:1 on flat ground contained and redirected the 8000S vehicle. The vehicle did not penetrate, under ride, or override the installation. Dynamic deflection in Test 4-12 with 3.2-m (10-foot, 6-inch) post spacing was reported by TTI to be 2.42m (8.0 feet).

The 4-cable barrier systems described above are acceptable for use on the designated 1V:4H or flatter slopes under NCHRP Report 350 Test Level 3 or 4 conditions as noted. The systems are detailed in the enclosed drawings and are acceptable for use on the NHS when such use is

Findings
The 4-cable barrier systems described above are acceptable for use on the designated 1V:4H or flatter slopes under NCHRP Report 350 Test Level 3 or 4 conditions as noted. The systems are detailed in the enclosed drawings and are acceptable for use on the NHS when such use is acceptable to a highway agency.

Although the barrier performed well under idealized test impact conditions, 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 6m (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,

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

 

Sincerely yours,

/* Signature of David A. Nicol */

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

Enclosures

`
General Information Impact Conditions Post-Impact Trajectory
 Test Agency Texas Transportation Institute Speed 49.6 mi/h Stopping Distance 348 ft dwnstrm
46 ft twd traffic
 Test No. 400001-TCR33 Angle 13.6 degrees Vehicle Stability  
 Date 2009-09-04Location/Orientation 1 ft upstream Maximum Yaw Angle -23 degrees
Test Article Exit Conditions Post 16 Maximum Pitch Angle -3 degrees
 Type Longitudinal Barrier Speed Not obtainable Maximum Roll Angle 1 degrees
 Name Trinity CASS Angle Not obtainable Vehicle Snagging No
 Installation Length 343.5 ft. Occupant Risk Values Vehicle Pocketing No
 Material or Key Element 4 wire ropes supported by slotted S3x5.7 support posts spaced at 10 ft-6 inches Impact Velocity Test Article Deflections
Soil Type and Condition Concrete footings in crushed limestone, dry Longitudinal 3.6 ft/s Dynamic ~8 ft
Test Vehicle   Lateral 4.9 ft/s Permanent 0.9 ft
 Type/Designation 8000s Ridedown Accelerations  
 Make and Model 1994 International NaviStar 4700 Longitudinal -1.4 G Working Width 9.1 ft
 Curb 12,400 lb Lateral -1.3 G Vehicle Damage  
 Test Inertial 17,710 lb THIV 6.4 km/h VDS 01RFQ1
 Dummy No dummy PHD 0.12 CDC 01RFEW1
 Gross Static 17,710 lb Max. 0.050-s Average   Max. Exterior Deformation 1.5 inches
  Longitudinal -06.g Max. Exterior Deformation 1.5 inches
  Lateral -1.1G  
  Vertical 0.4 G  

Figure 15. Summary of results for NCHRP Report 350 test 4-12 on the Trinity CASS on level ground.

General Information Impact Conditions Post-Impact Trajectory
 Test Agency Texas Transportation Institute Speed 60.4 mi/h Stopping Distance 214 ft dwnstrm
30 ft twd traffic
 Test No. 400001TCR35 Angle 19.5 degrees Vehicle Stability
 Date 2009-10-08 Location/Orientation Midspan btw posts 15&16 Maximum Yaw Angle 32 degrees
Test Article Exit Conditions   Maximum Pitch Angle 9 degrees
 Type Cable Barrier Speed Not obtainable Maximum Roll Angle 14 degrees
 Name Trinity CASS Angle -3.6 degrees Vehicle Snagging No
 Installation Length 343.5 ft. Occupant Risk Values   Vehicle Pocketing No
 Material or Key Element CASS with S3x5.7 posts installed on 4H:1V forslope Impact Velocity Test Article Deflections  
Soil Type and Condition Concrete footings in Standard Soil, Damp Longitudinal 12.8 ft/s Dynamic 3.4 ft
Test Vehicle   Lateral 12.8 ft/s Permanent 0.1 ft
 Type/Designation 820C Ridedown Accelerations   Working Width 4.2 ft
 Make and Model 1995Suzuki Swift Longitudinal -5.3G Vehicle Damage  
 Curb 1881 lb Lateral 6.3 G VDS 11LFQ3
 Test Inertial 1850 lb THIV 18.2 km/h CDC 11FDEW3
 Dummy 167 PHD 7.5 G Max. Exterior Deformation 10.6 inches
 Gross Static 2017 lb Max. 0.050-s Average   Max.Occupant Compartment Deformation 0.6 inches
  Longitudinal -2.9 G    
  Lateral 4.3 G  
  Vertical 3.7 G  

Figure 16. Summary of results for NCHRP Report 350 test 3-10 on the Trinity CASS with S3x5.7 posts installed on a 4H:IV forslope.

General Information Impact Conditions Post-Impact Trajectory
 Test Agency Texas Transportation Institute Speed 63.7 mi/h Stopping Distance 425 ft dwnstrm
83 ft twd traffic
 Test No. 40000-1TCR32 Angle 25.4 degrees Vehicle Stability
 Date 2009-08-12 Location/Orientation At post 16 Maximum Yaw Angle 39 degrees
Test Article Exit Conditions   Maximum Pitch Angle -6 degrees
 Type Longitudinal Barrier Speed Out of view Maximum Roll Angle 28 degrees
 Name CASS on 4H:1V Slope Angle Not obtainable Vehicle Snagging No
 Installation Length 343.5 ft. Occupant Risk Values   Vehicle Pocketing Yes
 Material or Key Element CASS with S3x5.7 posts spaced at 10ft-6 inches on 4V:H1 forslope Impact Velocity   Test Article Deflections  
Soil Type and Condition Cruch Limestone, Dry Longitudinal 8.2 ft/s Dynamic 7.1 ft
Test Vehicle   Lateral 13.4 ft/s Permanent 0.5 ft
 Type/Designation 2270P Ridedown Accelerations   Working Width 8.2 ft
 Make and Model 2003 Dodge 1500 Quad Longitudinal -3.5G Vehicle Damage  
 Curb 4871 Lateral 4.3 G VDS 11LFQ1
 Test Inertial 5007 THIV 15.9 km/h CDC 11LFEW2
 Dummy No Dummy PHD 5.0 G Max. Exterior Deformation 10.6 inches
 Gross Static 5007 Max. 0.050-s Average   Max.Occupant Compartment Deformation 0
  Longitudinal -2.0 G    
  Lateral 3.5 G  
  Vertical -2.9 G  

Figure 11. Summary of results for NCHRP Report 350 test 3-11 on CASS with S3x5.7 posts on 4H:IV forslope.

General Information Impact Conditions Post-Impact Trajectory
 Test Agency Texas Transportation Institute Speed 63.6 mi/h Stopping Distance 73.5 ft dwnstrm
Within cables
 Test No. 400001-TCR32 Angle 25.4 degrees Vehicle Stability
 Date 2009-11-08 Location/Orientation At post 13 Maximum Yaw Angle 32 degrees
Test Article Exit Conditions   Maximum Pitch Angle -12 degrees
 Type Wire Rope Barrier Speed Out of view Maximum Roll Angle -57 degrees
 Name CASS with S3x5.7 posts/4H:1V foreslope Angle Out of view Vehicle Snagging No
 Installation Length 343.5 ft. Occupant Risk Values   Vehicle Pocketing No
 Material or Key Element CASS with S3x5.7 posts installed 4V:1V forslope Impact Velocity   Test Article Deflections  
Soil Type and Condition Standard Soil, Dry Longitudinal 8.8 ft/s Dynamic 8.5 ft
Test Vehicle   Lateral 12.5 ft/s Permanent 3.0 ft
 Type/Designation 2270P Ridedown Accelerations   Working Width 9.8 ft
 Make and Model 2004 Dodge Ram1500 Quad-Cab Longitudinal -4.1G Vehicle Damage  
 Curb 4772 lb Lateral 5.9 G VDS 11LFQ2
 Test Inertial 5026 lb THIV 15.2 km/h CDC 11DEW2
 Dummy No Dummy PHD 6.1 G Max. Exterior Deformation 7.5 inches
 Gross Static 5026 lb Max. 0.050-s Average   Max.Occupant Compartment Deformation 0
  Longitudinal -2.0 G    
  Lateral 3.6 G  
  Vertical -1.8 G  

Figure 16. Summary of results for NCHRP Report 350 test 3-11 on the CASS with S3x5.7 posts installed on 4H:IV forslope.

General Information Impact Conditions Post-Impact Trajectory
 Test Agency Texas Transportation Institute Speed entering ditch 63.4 mi/h Stopping Distance 35 ft dwnstr
11 ft field side
 Test No. 40000-1TCR34 Angle entering ditch 20.8 degrees Vehicle Stability
 Date 2009-10-12 Speed at wire rope 60.8 mi/h Maximum Yaw Angle -172 degrees
Angle at wire rope 24.0 degrees
Location/Orientation Mispan 13-14
Test Article Exit Conditions   Maximum Pitch Angle 26 degrees
 Type Median Barrier Speed Out of view Maximum Roll Angle -34 degrees
 Name Trinity CASS Angle Out of view Vehicle Snagging Yes
 Installation Length 342 ft. Occupant Risk Values   Vehicle Pocketing No
 Material or Key Element S3x5.7 posts installed on a 4H:1V backslope Impact Velocity   Test Article Deflections  
Soil Type and Condition Concrete footings in standard soil, damp Longitudinal 18.7 ft/s Dynamic 4.4 ft
Test Vehicle   Lateral 2.3 ft/s Permanent 1.9 ft
 Type/Designation 820C Ridedown Accelerations   Working Width 5.2 ft
 Make and Model 1997 Geo Metro Longitudinal -8.9 G Vehicle Damage  
 Curb 1797 lb Lateral -8.6 G VDS 11LFQ4
 Test Inertial 1861 lb THIV 19.2 km/h CDC 11FLEW3
 Dummy 165 lb PHD 11.9 G Max. Exterior Deformation 9.8 inches
 Gross Static 2026 lb Max. 0.050-s Average   Max.Occupant Compartment Deformation 1.2 inches
  Longitudinal -7.8G    
  Lateral -4.4 G  
  Vertical -5.4 G  

Figure 15. Summary of results for NCHRP Report 350 test 3-10
on the Trinity CASS with S3x5.7 posts installed on a 4H:IV backslope.

Page last modified on August 16, 2011.
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