Mr. Bill Neusch, President 

 Gibraltar 

 320 Southland Road 

 Burnet, Texas 78611 

Dear Mr. Neusch: 

In your May 30 letter to Mr. Richard Powers of my staff, you requested the Federal Highway 

Administration (FHWA) acceptance of a high-tension, 3-strand cable barrier system. Copies of 

a May 26 report prepared by Karco Engineering and entitled “Crash Test Report for Gibraltar 

Tested to National Cooperative Highway Research Program (NCHRP) Report 350 

Recommendations for test level 3-10 and 3-11 Cable Barrier System” and digital videos of the 

two tests were also submitted. 

Your cable barrier system consists of three 3⁄4-inch 3 X 7 prestretched, post-tensioned 

galvanized steel cables supported by steel C-posts 3.25 x 2.5 x 0.15-inches thick and 4-ft long, 

set in HSS 4 x 3 x 3/16 sockets. These sockets were 15-inches deep and placed in reinforced 

concrete footings 42-inches deep and 12-inches in diameter. Post spacing was 15 feet on 

centers. The posts were installed on alternate sides of the 3 cables that are held in place by a 

7/16-inch diameter x 24-inch long galvanized steel hairpin and lock plate, with which the 

bottom, middle, and top cable heights are set and held in place at above-ground heights of 

20 inches, 25 inches and 30 inches, respectively. These details for the line posts are shown in 

Enclosure 1. This enclosure also includes drawings of the terminal you developed for use with 

the Gibraltar Cable Barrier, which will be addressed in a separate acceptance letter in the 

immediate future. The barrier test installation was 200 feet long and each cable was tensioned 

to 4800 lbs. prior to the tests. 

The NCHRP Report 350 tests 3-10 and 3-11 were both successfully conducted and the 

summary results of each are shown in Enclosure 2. Dynamic deflection was reported to be 

8.5 feet. Based on the test results, the Gibraltar Cable Barrier may be considered an NCHRP 

Report 350 traffic barrier at test level 3 as a median barrier when the posts are set an alternate 

sides of the cables or as a roadside barrier when the cables are all on the traffic side of the 

C-posts. 

400 Seventh St., S.W. 

Washington, D.C. 20590

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

June 13, 2005 
2

You also asked about the acceptability of an alternative post embedment detail and the effect 

additional tension in the cables might have on the dynamic deflection of your barrier. 

Regarding post embedment details, a 30-inch deep reinforced concrete footing can be used 

when a mowing strip is used under the barrier. While longer posts embedded directly into the 

ground would almost certainly work, other factors such as post type and spacing, the use of soil 

plates, soil conditions, the distance between adjacent terminals or anchors, and the method 

used to connect the cables to the posts will affect the deflection distance and there is currently 

no way to predict that deflection with any degree of confidence. Similarly, increasing the cable 

tension will intuitively decrease deflection, but any such decrease cannot be readily quantified 

as it, too, is dependent on the factors listed above. To determine the design deflections for 

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

longitudinal barriers are only a reasonable approximation of what may be seen in the field. 

Because they are the observed results of a single test, actual deflections for any specific barrier 

can be much more or much less, depending on the size, speed, and impact angle of the vehicle 

that strikes it. In locations where deflection is a critical design element, a rigid concrete barrier 

would be a more logical choice than a flexible or semi-flexible barrier type. 

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. 

• 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-137 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 
3

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/ 

John R. Baxter, P.E. 

 Director, Office of Safety Design 

 Office of Safety 

2 Enclosures 

FHWA:HSA-10:DPowers:tb:x61320:6/13/05 

File: h://directory folder/dpowers/B137(GibraltarWR) 

cc: HSA-10 (Reader, HSA-1; Chron File, HSA-10; 

 D.Powers, HSA-10) 

9 

DATA SHEET NO. 3 

SUMMARY OF RESULTS FOR TEST NO. 3-10

GENERAL INFORMATION OCCUPANT RISK VALUES 

TEST AGENCY KARCO ENGINEERING IMPACT VELOCITY (m/sec) 

TEST NO. 3-10 X-DIRECTION 

DATE 05/26/05 Y-DIRECTION 

TEST ARTICLE THIV (optional) 

TYPE LONGITUDINAL FENCE BARRIER UNIT RIDEDOWN ACCELERATION (g’s) 

INSTALLATION LENGTH (m) N/A X-DIRECTION 

SIZE AND/OR DIMENSION OF KEY ELEMENTS 200 ft LON Y-DIRECTION 

SOIL TYPE AND CONDITION CONCRETE PHD (optional) 

TEST VEHICLE 820C ASI (optional) 

TYPE PRODUCTION TEST ARTICLE DEFLECTIONS (m) 

DESIGNATION 3-10 DYNAMIC 

MODEL CHEVROLET METRO 2-DOOR PERMANENT 

MASS (CURB) 807 Kg (1780 Ibs) VEHICLE DAMAGE 

MASS (TEST INERTIAL) 827 Kg (1823 Ibs) EXTERIOR 

DUMMY(s) MASS 75 kg (165 lbs.) VDS 

GROSS STATIC WEIGHT 895 Kg (1974 Ibs) CDC 

IMPACT CONDITIONS INTERIOR 

SPEED (km/h) 100.2 (62.9 mph) OCDI 

ANGLE (Deg.) 20 

IMPACT SEVERITY (kJ) 41.3 POST IMPACT VEHICULAR BEHAVIOR 

EXIT CONDITIONS MAXIMUM ROLL ANGLE (Deg.) 

SPEED (km/h) 79 (49.2 mph) MAXIMUM PITCH ANGLE (Deg.) 

ANGLE (Deg.) 0 MAXIMUM YAW ANGLE (Deg.) 
9 

DATA SHEET NO. 3 

SUMMARY OF RESULTS FOR TEST NO. 3-11

GENERAL INFORMATION OCCUPANT RISK VALUES 

TEST AGENCY KARCO ENGINEERING IMPACT VELOCITY (m/sec) 

TEST NO. 3-11 X-DIRECTION 

DATE 5/26/05 Y-DIRECTION 

TEST ARTICLE THIV (optional) 

TYPE LONGITUDINAL FENCE BARRIER UNIT RIDEDOWN ACCELERATION (g’s) 

INSTALLATION LENGTH (m) N/A X-DIRECTION 

SIZE AND/OR DIMENSION OF KEY ELEMENTS Y-DIRECTION 

SOIL TYPE AND CONDITION CONCRETE PHD (optional) 

TEST VEHICLE 2000P ASI (optional) 

TYPE PRODUCTION TEST ARTICLE DEFLECTIONS (m) 

DESIGNATION 3-11 DYNAMIC 

MODEL GMC SIERRA 2-DOOR TRUCK PERMANENT 

MASS (CURB) 2244 Kg (4948 Ibs) VEHICLE DAMAGE 

MASS (TEST INERTIAL) 2065 Kg (4552 Ibs) EXTERIOR 

DUMMY(s) MASS N/A VDS 

GROSS STATIC WEIGHT 2065 Kg (4552 Ibs) CDC 

IMPACT CONDITIONS INTERIOR 

SPEED (km/h) 102.4 km/h (63.7 mph) OCDI 

ANGLE (Deg.) 25 

IMPACT SEVERITY (kJ) 149.2 POST IMPACT VEHICULAR BEHAVIOR 

EXIT CONDITIONS MAXIMUM ROLL ANGLE (Deg.) 

SPEED (km/h) 48 (29.8 mph) MAXIMUM PITCH ANGLE (Deg.) 

ANGLE (Deg.) N/A MAXIMUM YAW ANGLE (Deg.)