Mr. Stephen L. Brown 

 President 

 Trinity Highway Safety Products, Inc. 

 P.O. Box 568887 

 Dallas, Texas 75356-8887 

Dear Mr. Brown: 

In two separate letters to Mr. Richard Powers, both dated November 15, Mr. Brian Smith 

requested the Federal Highway Administration (FHWA) acceptance of modified designs of 

your CASS cable barrier, one at test level 3 (TL-3) and one at TL-4. Both designs use S4 x 7.7 

structural steel posts to support the high-tensioned cables in lieu of the original CASS 

C-channel posts. For the TL-3 design, the 3/4-inch diameter cables were set at heights of 21.0, 

25.2, and 29.5 inches above the ground surface, measured to the center of each cable. The slot 

design was also modified and the 47.25-inch long posts were weakened by the addition of two 

11/16-inch diameter holes through each flange at ground line. These details are shown in 

Enclosure 1. 

To verify the crashworthiness of the modified CASS design, two initial tests were conducted 

on a prototype TL-3 design at the Southwest Research Institute in San Antonio, details of 

which were contained in that agency’s September 1, final report entitled “Full-Scale Crash 

Evaluation of a Tensioned Safety System (TESS) Cable Barrier System – NCHRP Report 350 

Tests 3-10 and 3-11”. For these tests, the weakening holes in each line post were 9/16-inch 

diameter and the posts were set on 16’-8” centers. The wire ropes were pretensioned to 5600 

pounds. As seen on the test summary sheets (Enclosure 2a and 2b), both tests met the National 

Cooperative Highway Research Program (NCHRP) Report 350 evaluation criteria, but there 

was more damage to the small car and more post-crash instability with the pickup truck than 

normally seen in cable barrier tests. You subsequently increased the hole size to 11/16 inch 

and increased the post spacing to 20 feet. This final design was tested at the Texas 

Transportation Institute (TTI) with the pickup truck as described in that agency’s November

2005 report, “NCHRP Report 350 Test 3-11 of the Trinity CASS-TL3 Spaced at 6.1 m in 

Concrete Footings and Sockets with Non-Pre-Stretched Cable”. These test results, shown in 

400 Seventh St., S.W. 

Washington, D.C. 20590

In Reply Refer To: HSA-10/B-141 

November 17, 2005 
2

Enclosure 3, were a significant improvement over the first 3-11 test, and I agree that test 3-10 

need not be run on the final “softer” design. The design deflection for the 100-m long test 

installation was 7.7 feet. All line posts were set into 5-inch x 3-inch x 11 gauge sockets 

encased in 12-inch diameter x 30-inch deep reinforced concrete foundations.

The TTI also tested the modified CASS with a single-unit truck under TL-4 impact conditions 

and reported the successful results in its November 2005 report entitled, “NCHRP Report 350 

Test 4-12 of the Trinity CASS-TL4 Spaced at 6.1 m in Concrete Footings and Sockets with 

Non-Pre-Stretched Cable”. Enclosure 4 is the summary sheet for this test. The support posts 

were lengthened to approximately 56 inches and the cable heights were set at 21.0, 29.5, and 

38.0 inches. Thus, the bottom cable height remained the same as in the TL-3 design, and the 

middle cable was the same height as the upper cable in the TL-3 design. Since only the top 

cable was raised, it is reasonable to assume that the TL-4 design would perform acceptably in 

tests 3-10 and 3-11, both of which can be waived. The CASS TL-4 uses the same TL-3 anchor 

developed for the original CASS barrier (FHWA acceptance letter CC-76), and is identical 

through post 7. Two longer posts are then added to transition the cables gradually to the higher 

CASS TL-4 cable heights. This design is shown in Enclosure 5. Finally, since the design 

deflection of longitudinal barrier systems is based on the pickup truck test, which was waived 

for the CASS TL-4, its dynamic deflection can be assumed to be the same as the CASS TL-3, 

i.e., 7.7 feet. As with all roadside safety features, the field performance of both designs should 

be closely monitored to verify acceptable performance under varied field conditions. 

The CASS TL-3 and CASS TL-4 designs described above may be used as either a roadside or 

median barrier on the National Highway System (NHS) when such use is acceptable to the 

contracting agency. Although the cables used in the test were not pre-stretched, this 

acceptance is also valid if and when pre-stretched cables are used, assuming that the 

recommended post-tensioning is applied to the barrier. You also asked about the acceptability 

of an alternative post embedment detail, specifically direct-driven posts or posts set in driven 

sockets. While longer posts embedded directly into the ground or posts in sockets without 

concrete foundations would probably perform satisfactorily, there is currently no way to 

predict barrier deflection with different embedment designs. To determine the design 

deflections for alternative post designs, testing would need to be done. 

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

• Our acceptance is limited to the crashworthiness characteristics of the CASS TL-3 and 

TL-4 designs and does not cover their structural features, durability, or maintenance 

characteristics. 

• Any design or material changes that may adversely affect the crashworthiness of the 

barrier will require a new acceptance letter. 

• Should the FHWA discover that the qualification testing was flawed, that in-service 

performance reveals unacceptable safety problems, or that the barrier being marketed is 

significantly different from the version that was crash tested, it reserves the right to 

modify or revoke its acceptance. 

• You will be expected to supply potential users with sufficient information on design and 

installation requirements to ensure proper performance. 
3

• You will be expected to certify to potential users that the hardware furnished has 

essentially the same chemistry, mechanical properties, and geometry as that submitted for 

acceptance. 

• To prevent misunderstanding by others, this letter of acceptance, designated as number 

B-141 shall not be reproduced except in full. This letter, and the test documentation upon 

which this letter is based, is public information. All such letters and documentation may 

be reviewed at our office upon request. 

• The CASS Cable Barrier includes patented components and is considered proprietary. 

When proprietary devices are specified by a highway agency for use on Federal-aid 

projects, except exempt, non-NHS projects, they: (a) must be supplied through 

competitive bidding with equally suitable unpatented items; (b) the highway agency must 

certify that they are essential for synchronization with existing highway facilities or that 

no equally suitable alternative exists or; (c) they must be used for research or for a 

distinctive type of construction on relatively short sections of road for experimental 

purposes. Our regulations concerning proprietary products are contained in Title 23, 

Code of Federal Regulations, Section 635.411. 

Sincerely yours, 

 

 /original signed by George Ed. Rice, Jr./ 

 ~for~ 

John R. Baxter, P.E. 

 Director, Office of Safety Design 

 Office of Safety 

5 Enclosures 
DETAIL A

1

1

2

2

A A

B B

REV

CHK:

DRW:

SHIPPING WT:

GALV SPEC:

PROJ.

TRINITY INDUSTRIES, INC.

HIGHWAY SAFETY DIVISION

DWG NO:

TL3-S11 0

31.3 lb

A123

CASS-TL3

E.A.S

CASS-TL3 - SHORT POST

3'-11 1/4" - (IN CONCRETE

OR IN DRIVEN SLEEVE) 7/16/2005

R.M.H. 7/18/2005

A

BILL OF MATERIAL

QTY PART No ITEM DESCRIPTION LENGTH Lbs / Each MATERIAL

1 1 S 4 x 7.7 3'-11 1/4" 29.54 A36

3'-11 1/4" S

4

x

7.7

x

2

15/16"

R13/32"

13/16"

1 3/8"

13/16"

1 3/8"

13/16"

5/8" 4

5 1/ 6" 4

5 1/ 6"

2

2

5/3

2"

11 13 1/ 6"

2"

(4")

2'-8 1/4"

4

5 1/ 6" 4

5/16"

3/4"

1 1/2"

n11/16" (2)

HOLES THRU

IN LINE.

1
DETAIL A

1

1

2

2

A A

B B

REV

CHK:

DRW:

SHIPPING WT:

GALV SPEC:

PROJ.

TRINITY HIGHWAY SAFETY

PRODUCTS, INC.

DWG NO:

TL4-S11 0

36.6 lb

A123

CASS-TL4

E.A.S

CASS-TL4 - SHORT POST

4'-7 7/8" - (IN CONCRETE

OR IN DRIVEN SLEEVE) 10/14/2005

B.S. 10/14/2005

A

BILL OF MATERIAL

QTY PC NO. ITEM DESCRIPTION LENGTH Lbs / Each MATERIAL

1 1 S 4 x 7.7 4'-7 7/8" 34.56 A36

3/4"

1 1/2"

4'-7

7

8/ " S

4

x

7

7. x

n11/16" (2)

HOLES THRU

IN LINE.

R13/32"

5/8" 1'-5 1/4" (4) S

P

A

C

E

S

A

T

4

5 1/ 6" =

2

2

5/3

2"

2"

(4")

1'-5 1/4" (4) S

P

A

C

E

S

A

T

4

5 1/ 6" =

13/16"

15/16"

1 3/8"

13/16"

1 3/8"

13/16"

1 3/8"

13/16"

1 3/8"

13/16"

1'-8

7 1/ 6"

3'-4

7

8/ "

1
D-1 

Table D.1 – Test CASS-2 Summary Report 

 Test Summary Report 

General Information 

 Test Agency: Southwest Research Institute 

 Test Number: CASS-2 

 Test Date: 08/17/05 

 Test Article: TESS Cable Barrier 

Test Vehicle 

 Description: 2000 Suzuki Swift 

 Test Inertial Mass: 907 kg 

 Gross Static Mass: 907 kg 

Impact Conditions 

 Speed: 100.0 km/hr 

 Angle: 20.0 degrees 

Occupant Risk Factors 

 Impact Velocity (m/s) at 0.1820 seconds on left side of interior 

 x-direction 3.4 

 y-direction -4.5 

 THIV (km/hr): 24.6 at 0.1919 seconds on left side of interior 

 THIV (m/s): 6.8 

 Ridedown Accelerations (g's) 

 x-direction -6.2 (0.2722 - 0.2822 seconds) 

 y-direction 6.8 (0.1817 - 0.1917 seconds) 

 PHD (g's): 7.0 (0.2722 - 0.2822 seconds) 

 ASI: 0.64 (0.1617 - 0.2117 seconds) 

Max. 50msec Moving Avg. Accelerations (g's) 

 x-direction -3.9 (0.2574 - 0.3074 seconds) 

 y-direction 5.3 (0.1617 - 0.2117 seconds) 

 z-direction -1.9 (0.1742 - 0.2242 seconds) 

Max Roll, Pitch, and Yaw Angles (degrees) 

 Roll -5.1 (0.2038 seconds) 

 Pitch -7.1 (0.3884 seconds) 

 Yaw -15.8 (0.3318 seconds) 
C-1 

Table C.1 – Test CASS-1 Summary Report 

General Information 

 Test Agency: Southwest Research Institute 

 Test Number: CASS-1 

 Test Date: 08/16/05 

 Test Article: TESS Cable Barrier 

Test Vehicle 

 Description: 3/4 Ton Chevrolet Pickup 

 Test Inertial Mass: 2000 kg 

 Gross Static Mass: 2000 kg 

Impact Conditions 

 Speed: 100.0 km/hr 

 Angle: 25.0 degrees 

Occupant Risk Factors 

 Impact Velocity (m/s) at 0.2023 seconds on right side of interior 

 x-direction 2.2 

 y-direction 3.5 

 THIV (km/hr): 16.8 at 0.2106 seconds on right side of interior 

 THIV (m/s): 4.7 

 Ridedown Accelerations (g's) 

 x-direction -3.3 (0.2092 - 0.2192 seconds) 

 y-direction -7.6 (0.3611 - 0.3711 seconds) 

 PHD (g's): 7.7 (0.3611 - 0.3711 seconds) 

 ASI: 0.49 (0.3437 - 0.3937 seconds) 

Max. 50msec Moving Avg. Accelerations (g's) 

 x-direction -1.9 (0.1892 - 0.2392 seconds) 

 y-direction -4.4 (0.3432 - 0.3932 seconds) 

 z-direction 2.0 (0.5184 - 0.5684 seconds) 

Max Roll, Pitch, and Yaw Angles (degrees) 

 Roll -26.9 (0.7841 seconds) 

 Pitch 10.9 (0.5694 seconds) 

 Yaw 30.7 (0.4670 seconds) 
22 

0.000 s 0.244 s 0.488 s 

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 Institute 400001-TCR8 10-07-2005 Cable Guardrail Trinity CASS-TL3 101.9 3 Wire Ropes With S4x7.7# I-Beam Posts In Concrete Socketed Footings Spaced at 6.1 m Standard Soil, Dry Production 20000P 1999 Chevrolet C2500 2223 2106 N/A 2106 

Impact Conditions  Speed (km/h) ............................. Angle (deg) ................................Exit Conditions Speed (km/h) ............................. Angle (deg) ................................Occupant Risk Values

Impact Velocity (m/s) 

 Longitudinal ............................ Lateral .................................... THIV (km/h) ...............................

Ridedown Accelerations (g’s) 

 Longitudinal ............................ Lateral .................................... PHD (g’s) ................................... ASI ............................................Max. 0.050-s Average (g’s)  Longitudinal ............................ Lateral .................................... Vertical ...................................

96.5 24.7 N/A N/A  2.1  3.4 13.1 -3.5  7.6  7.6 0.45 -1.6  4.1  2.2 

Test Article Deflections  Dynamic ..................... Permanent.................. Working Width............Vehicle Damage Exterior  VDS......................... CDC ........................ Max. Exterior 

 Vehicle Crush (mm

 Interior  OCDI ....................... Max. Occupant Com

 Deformation (mm)

Post-Impact Behavior

(during 1.0 sec after im

 Max. Yaw Angle (de

Max. Pitch Angle (deMax. Roll Angle (deg

Figure 15. Summary of results for NCHRP Report 350 test 3-11 on the Trinity CASS-TL3 at 6.1 m 
0.000 s 0.269 0.538 

Genera ormation

Test cy...............................Test ....................................

 Date ...................................Test A Type ...................................

Nam ...................................

Installation Length (m)...............

y Elements ..........

Soil Ty d Condition.............Test Vehicle Type........................................... Designation................................ Model......................................... Mass (kg) Curb........................................ Test Inertial............................. Dummy ................................... Gross Static............................

Texas Transportation Institute 400001-TCR9 10-26-2005 Cable Guardrail Trinity CASS-TL4 101.9 3 Wire Ropes With S4x7.7# I-BeamPosts In Concrete Socketed Footings Spaced at 6.1 mStandard Soil, Dry Production 8000S 1991 Ford F-7005602 8196 N/A 8196 

Impact Conditions  Speed (km/h) ............................. Angle (deg) ................................Exit Conditions Speed (km/h) ............................. Angle (deg) ................................Occupant Risk Values

Impact Velocity (m/s) 

 Longitudinal ............................ Lateral .................................... THIV (km/h) ...............................

Ridedown Accelerations (g’s) 

 Longitudinal ............................ Lateral .................................... PHD (g’s) ................................... ASI ............................................Max. 0.050-s Average (g’s)  Longitudinal ............................ Lateral .................................... Vertical ...................................

82.5 14.1 N/A N/A 1.3 2.0 8.2 -1.1  1.8  2.1 0.14 -0.7  1.3  0.8 

Test Article Deflectio  Dynamic Permanent Working Width............Vehicle Damage Exterior  CDC ........................ Max. Exterior 

 Vehicle Crush (mm

 Interior  Max. Occupant Com

 Deformation (mm)

Post-Impact Behavior

(during 1.0 sec after im

 Max. Yaw Angle (de

Max. Pitch Angle (deMax. Roll Angle (deg

Figure 16. Summary of results for NCHRP Report 350 test 4-12 on the Trinity CASS-TL4 spaced 

23 

l Inf

AgenNo.

........

rticle

........

e ......

Material or Ke

pe an

ns 

.....................

..................
Figure 5. Post details. 

9