Mr. Bill Neusch, President 

 Gibraltar 

 320 Southland Road 

 Burnet, Texas 78611 

Dear Mr. Neusch: 

In your August 11 letter to Mr. Richard Powers of my staff, you requested the Federal 

Highway Administration’s (FHWA) acceptance of a modified version of your TL-3 Gibraltar 

cable barrier system that was tested to the NCHRP Report 350 test level 4 (TL-4). Copies of 

the August 5 report prepared by Exponent Failure Analysis Associates in Phoenix, Arizona 

entitled “NCHRP Report 350 Test 4-12 of the Gibraltar Longitudinal Cable Barrier System” 

and digital videos of the test were also submitted. 

Your modified cable barrier system consists of three, 3/4-inch diameter 3 X 7 post-tensioned 

galvanized steel cables supported by steel C-posts 3.25 x 2.5 x 0.15-inches thick and 7-ft long, 

The posts, set on 14-foot centers, were driven to a depth of 3.5 feet and installed on alternate 

sides of the cables. The 3 cables are locked in place by a 7/16-inch diameter x 24-inch long 

galvanized steel hairpin and lock plate that fits inside each post. For your TL-4 design, the 

bottom, middle, and top cable heights are set at 20 inches, 30 inches and 39 inches, 

respectively. These details are shown in Enclosure 1, which also includes drawings of the 

terminal. This terminal is essentially identical to the TL-3 design developed for use with the 

original TL-3 Gibraltar Cable Barrier. The only modification needed in the terminal to match 

the higher cables in the TL-4 barrier design was the increased height of the center and top 

cables at terminal post 4. The barrier test installation was 350 feet long and each cable was 

tensioned to 4800 lbs. prior to the tests. 

The NCHRP Report 350 test 4-12 was successfully conducted and the summary results are 

shown in Enclosure 2. Dynamic deflection was reported to be 7 feet in the 350-foot long test 

installation. Since the bottom cable remained at the same height as the TL-3 design, we agreed 

beforehand that tests with the small car and the pickup truck could be waived. Based on the 

test results, the Gibraltar Cable Barrier as described herein may be considered an NCHRP 

Report 350 TL-4 median barrier when the posts are set on alternate sides of the cables or as a 

TL-4 roadside barrier when the cables are all on the traffic side of the C-posts. Shorter, 

socketed line posts, as shown in the enclosed drawing may be used in lieu of driven posts. 

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

• Our acceptance is limited to the crashworthiness characteristics of the tested device and 

does not cover its structural features, durability, or maintenance characteristics. 

400 Seventh St., S.W. 

Washington, D.C. 20590

In Reply Refer To: HSA-10/B-137A

September 9, 2005 
2

• 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. 

• 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, and that they will meet the crashworthiness requirements of the FHWA and 

the NCHRP Report 350. 

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

B-137A 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 Gibraltar 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 E. Rice, Jr./ 

 ~for~ 

John R. Baxter, P.E. 

 Director, Office of Safety Design 

 Office of Safety 

2 Enclosures 

Page 7 of 9 

TEST FINDINGS SUMMARY 

GENERAL INFORMATION OCCUPANT RISK VALUES 

TEST AGENCY EXPONENT IMPACT VELOCITY 

TEST NO. 4-12 X-DIRECTION (1) 

DATE 8/5/05 Y-DIRECTION (1) 

TEST ARTICLE GIBRALTAR CABLE 

BARRIER SYSTEM THIV (1) 

TYPE LONGITUDINAL 

BARRIER RIDEDOWN ACCELERATIONS 

INSTALLATION 

LENGTH 106.7 m (350 ft) X-DIRECTION (1) 

SOIL CLASSIFICATION 

 (AASHTO M145) & 

MOISTURE CONDITION 

A-4 

7.3% MOISTURE 

CONTENT 

Y-DIRECTION (1) 

TEST VEHICLE 8000S PHD (1) 

TYPE PRODUCTION ASI (1) 

DESIGNATION SINGLE-UNIT TRUCK TEST ARTICLE DEFLECTION 

MAKE/ MODEL INTERNATIONAL/ 4700 DYNAMIC (2) 

MASS (TEST INERTIAL) 8,000 kg (17,600 lb) PERMANENT (2) 

ATD OPTIONAL - NOT USED VEHICLE DAMAGE 

IMPACT SPEED 80 km/hr (49.7 mph) 

IMPACT ANGLE (Deg.) 15 

EXIT SPEED 

55.9 km/hr (34.7 mph) 

at 5 seconds after initial 

impact 

EXIT ANGLE LESS THAN 4-degrees 

ENGAGEMENT WITH THE BARRIER 

CAUSED MINIMAL FRONT-END BODY 

DAMAGE AT THE BUMPER AND THE 

LEFT FRONT WHEEL WELL AND 

HOOD. DUE TO A COLLISION WITH A 

CONCRETE BARRIER AFTER 

DISENGAGEMENT FROM THE TEST 

ARTICLE, IT WAS NOT POSSIBLE TO 

ASCERTAIN THE EXTERNAL DAMAGE 

CAUSED BY THE TEST ARTICLE. NO 

INTRUSION OR PENETRATION INTO 

THE OCCUPANT COMPARTMENT 

OCCURRED. 

POST IMPACT VEHICULAR BEHAVIOR 

MAXIMUM ROLL 

ANGLE 

4.4° LEFT DOWN, 

5.6° RIGHT 

DOWN 

MAXIMUM PITCH 

ANGLE 7.6° NOSE UP 

(1) Not a requirement for a 4-12 test, but the data was 

recorded to obtain these values upon request of the test 

sponsor, Gibraltar. 

(2) The test article yielded as designed, which controlled 

lateral displacement of the test vehicle to approximately 

2.13 m (7 ft) measured at the vehicle left rear outboard tire

MAXIMUM YAW 

ANGLE 15.9° TO RIGHT 

Figure 3: TEST FINDINGS SUMMARY