May 13, 2003 

Refer to: HSA-10/B-119 

Mr. Rodney A. Boyd 

Trinity Highway Safety Products Division 

P.O. Box 568887 

Dallas, Texas 75356-8887 

Dear Mr. Boyd: 

In his March 28, 2003, letter to Mr. Richard Powers of my staff, your representative, Mr. Don 

Johnson, requested formal Federal Highway Administration acceptance of a high-tension, wire 

rope traffic barrier called the Cable Safety System (CASS). Included with the letter were copies 

of a Texas Transportation Institute (TTI) report dated March 2003, entitled “National 

Cooperative Highway Research Project (NCHRP) Report 350 test 3-11 of the TRINITY CASS” 

and videotapes of the crash test. 

The CASS barrier described in the test report consisted of three 19-mm diameter, pre-stretched 

3 x 7 strand steel cables. Mounting heights were 530 mm, 640 mm, and 750 mm above the 

ground and each cable was tensioned to 24kN using turnbuckles attached to swaged threaded 

fittings on each end. These cables were supported by 1600-mm long, galvanized 100 x 50 x 

4 mm C-channels driven into a Report 350 standard soil on 3-m centers. As shown on 

Enclosure 1, the upper central section of the post web was removed to accept the cables, which 

are kept separated in a vertical plane by the insertion of plastic spacer blocks, a stainless steel 

strap, and a plastic cap over the top of each post. 

In test 3-11, the pickup truck impacted at 100.6 km/h near the mid-point of a 100-meter long test 

installation at 24.2 degrees. As seen on the test summary sheet (Enclosure 2), all Report 350 

evaluation criteria were met. The cable rail deflected 2.4 meters. 

In a supplementary letter dated April 25, 2003, Mr. Johnson provided additional information on 

CEN (European Committee for Standardization) test TB-11 on the CASS barrier. This test, 

which is similar to NCHRP Report 350 test 3-10, was run by the Spanish testing agency 

CIDAUT and documented in its October 10, 2002 report entitled “Test Report for Cable Safety 

System, CASS – EN 1317 test TB11.” Based on the similarity of these two tests and on the 

results of test TB-11, I will waive the requirement for running Report 350 test 3-10. 
2

Although the posts in the test installation were driven directly into the soil, you requested the 

use of posts set in steel tubes or posts set into concrete sockets as alternative designs. As long as 

the post failure mechanism remains essentially unchanged (i.e., post failure by bending at the 

ground line with minimal deflection below ground as in the test installation), these options are 

acceptable. The CASS barrier should ideally be introduced and ended with a crashworthy 

terminal such as the previously accepted TTI breakaway terminal for a high-tensioned cable 

barrier. If the TTI terminal is used, the first six posts beyond the third breakaway anchor post 

must be the same posts at the same spacing as were used in the terminal certification tests unless 

you repeat the appropriate tests using the CASS post at these locations. A non-crashworthy 

terminal may be used if both the upstream and downstream anchors are adequately shielded. 

In summary, the CASS barrier, as described above, meets NCHRP Report 350 evaluation criteria 

as a test level 3 barrier and may be used on the National Highway System (NHS) as either a 

roadside or median barrier when such use is acceptable to the contracting agency. Since it is a 

proprietary product, the provisions of Title 23, Code of Federal Regulations, Section 635.411 

apply to its use on Federally funded projects, except exempt non-NHS projects. 

This Acceptance Letter shall not be construed as authorization or consent by the Federal 

Highway Administration to use, manufacture, or sell any patented device. The Acceptance 

Letter is limited to the crashworthiness characteristics of the candidate device, and the FHWA is 

neither prepared nor required to become involved in issues concerning patent law. Patent issues, 

if any, are to be resolved by the applicant. 

Sincerely yours, 

(original signed by Michael S. Griffith) 

 

Michael S. Griffith 

 Acting Director, Office of Safety Design 

 Office of Safety 

2 Enclosures 
6 

Details of the CASS post. 

1 in = 1 ft = 
21 

Summary of results for test 400001-TCR1 (CASS w/3 m spacing), NCHRP Report 350 test 3-

0.000 s 0.193 s 0.725 s 2.1

General Information

Test Agency . . . . . . . . . . . . . Test No. . . . . . . . . . . . . . . . . Date . . . . . . . . . . . . . . . . . . . 

Test Article

Type . . . . . . . . . . . . . . . . . . . Name . . . . . . . . . . . . . . . . . . Installation Length (m) . . . . . Material or Key Elements . . . 

Soil Type and Condition . . . . Test Vehicle

Type . . . . . . . . . . . . . . . . . . . Designation . . . . . . . . . . . . . Model . . . . . . . . . . . . . . . . . . Mass (kg)

Curb . . . . . . . . . . . . . . . . . Test Inertial. . . . . . . . . . . . Dummy. . . . . . . . . . . . . . . Gross Static . . . . . . . . . . . 

Texas Transportation Institute400001-TCR101/08/03GuardrailTrinity Cable Safety System (CASS)101.93 Wire Ropes Supported By C-ChannelMild Steel Support PostsStandard Soil, DryProduction2000P1998 Chevrolet 2500 Pickup20772045 N/A2045

Impact Conditions

Speed (km/h) . . . . . . . . . . . . . . . . Angle (deg) . . . . . . . . . . . . . . . . . 

Exit Conditions

Speed (km/h) . . . . . . . . . . . . . . . . Angle (deg) . . . . . . . . . . . . . . . . . 

Occupant Risk Values

Impact Velocity (m/s)

x-direction . . . . . . . . . . . . . . . . y-direction . . . . . . . . . . . . . . . . 

THIV (km/h) . . . . . . . . . . . . . . . . . Ridedown Accelerations (g's)

x-direction . . . . . . . . . . . . . . . . y-direction . . . . . . . . . . . . . . . . 

PHD (g’s) . . . . . . . . . . . . . . . . . . . ASI . . . . . . . . . . . . . . . . . . . . . . . Max. 0.050-s Average (g's)

x-direction . . . . . . . . . . . . . . . . y-direction . . . . . . . . . . . . . . . . z-direction . . . . . . . . . . . . . . . . 

100.6 24.213.9 9.4  2.7 3.514.7-3.9-5.1 5.2 0.37-2.2 3.2 1.5

Test Article Deflections (

Dynamic . . . . . . . . . . . Permanent . . . . . . . . . Working Width . . . . . . 

Vehicle Damage

Exterior

VDS . . . . . . . . . . . . CDC . . . . . . . . . . . . 

Maximum Exterior

Vehicle Crush (mm) 

Interior

OCDI. . . . . . . . . . . . 

Max. Occ. Compart.

Deformation (mm) . . 

Post-Impact Behavior

(during 1.0 s after impacMax. Yaw Angle (deg). Max. Pitch Angle (deg) Max. Roll Angle (deg) .