1200 New Jersey Avenue, SE. 

Washington, DC 20590 January 8, 2008 

In Reply Refer To: HSSD/B-137C 

Mr. Bill Neusch 

President 

Gibraltar 

320 Southland Road 

Burnet, TX 78611 

Dear Mr. Neusch: 

Thank you for your letter of October 19, 2007, requesting a modification to the anchorage of 

your company’s 4-cable barrier. Your original test level 4 (TL-4) Gibraltar cable barrier was 

formally accepted for use on the National Highway System (NHS) in the September 9, 2005, 

Federal Highway Administration (FHWA) acceptance letter B-137A. The tested design, as 

described in that letter, consisted of cables placed 20 inches, 30 inches, and 39 inches above the 

ground line. 

In our October 27, 2006, letter B-137A1 we accepted your 4-cable design having the lower three 

cables at the same heights as your TL-3 design while retaining the top cable at the tested TL-4 

height of 39 inches. The addition of the fourth cable required a modified "hairpin" and lock plate 

to retain the cables at the proper heights. In order to "anchor" the added cable you tapered that 

25-inch high cable down to the bottom (20-inch) cable between the first line post and the last 

terminal post and connected the two cables with a series of four cable clamps. Because of 

concerns raised over this splicing treatment, especially on downstream terminals, you have 

proposed to anchor each of the four cables separately. 

The modified anchor is shown on the enclosed drawings for reference and features the fourth 

cable attached directly to the anchor post foundation plate instead of being cable clamped to the 

bottom cable. You also added a fourth J-bolt to each terminal post to accommodate the fourth 

cable. We concur in this modification and find it acceptable for use with your four-cable barrier. 

The modified Gibraltar Cable Barrier as described above remains a National Cooperative 

Highway Research Program (NCHRP) Report 350 TL-4 median barrier when the posts are set on 

alternate sides of the cables or a TL-4 roadside barrier when the cables are all on the traffic side 

of the C-posts. 

Although the barrier performed well under ideal test impact conditions when originally crash 

tested, 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 
2

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, and when distances between anchorages exceed the 350-foot 

test length. 

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

• This acceptance is limited to the crashworthiness characteristics of the device(s). 

• Any changes that may adversely influence the crashworthiness of the device 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 device 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-137C, 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 four-cable Gibraltar Cable Barrier System is a patented product and considered 

proprietary. If 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 the 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. 

• This acceptance letter shall not be construed as authorization or consent by the FHWA to use, 

manufacture, or sell any patented device for which the applicant is not the patent holder. 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, 

David A. Nicol, P.E. 

Director, Office of Safety Design 

Office of Safety 

Enclosures 
- (4, Ancho' TO'M'noi Fitting

[8SJ C B. S. Te"inOI, Longth 27'-6'

,'-3' I 6'-3' i 1'-6~

3/4' Dlo. Ho,". foe

5/8' D'o. Ae,choes

BASE-PLATED POST Foe U.. Dn Cor,ceete 5/8' Mochonlcol Anc»oe

>lin Pullout Sk.ngth 10,000 lbs.

\ :-6

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~,

,0 L'ne

0

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c

i- x 9'-lO'

()2> _4 Ring. x 18' DIA

Ter"1ino.l Post

I- Begln Length of No.d foe SysteM . . Beg'n Poy .eng'h foe S..t.n -6~""

(4) 3/4' ""ee Rope.. Mo.lnUM IDDO' b.tw.." ,plic..

hj;.iv:.~s';e TSg"k.ted'

Atternote posts for "edM boeeiee InstoUo"on CObl. Refeeence Une

3_I/

ID.1 I I,

"'2-112"-":

~ ~ 3/4' TIB Cubt. Splic. Fitting

Ell ~= mm ~;J C-Soc"on 3/4' Teenlnot fltt;ng Post

HOlep'e

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I LOCk Plo te

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42'

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1--12,-1

line Post<Socketed) Line Post <Driven)

Cable Release

Anchor Post

>30'xt2' Conceete Fo",ndatlon w"h HI" 18' wid. >1owSteip

>42'x12' D.ep wlo >1owSteip

:REV,

"''''''''',''''''

[DATE' 10/23/07 !APPROVER,RF '.."-'--....... .. ,..,-

GENERAL NOTES

roe od"'tlonot Infoenotion con'oct Glbroltoe, Inc. ot 1-8DD-495-8957.

oe ..e .th. noeu'octu..'s peoduct nOMuol.

2. AU conce..e sholl b. nlnlnun 2500 PSI.

3. A"ee"ote Po", 'oe bI-d'eect'onai teoHlc "ow.

tf 'nstoU.d for troHic In on. direction

."stoU cobles on teo'flc sid. of posts.

4. Th. Cobte Boreler SysteM sno" be Instolle" on

shouldees oe on nedlons with ,'ope$ of 6<1or

nottee, If ",.tone" on $Iop.s steeper t"on 6.) up to '.) the 11.-4 systen perforns os 0 1l..3 ond Glbrolto. nust b. con'toctd for vorlous gui..onn.. eeloted to plocen.nt.

5. Th. Coble Boedee Syste" Is o«epted by the rH"'A

Tost levet - 4

6. S.e tho HUTCD 'oe p.oper 'Boerle.' detin.otlon

7. RoCk Ctouse' "'he.e soli" rock I. enCountoeeo, 0,) ror socketed post, continue "'QQ'ng 12' .'onetee, 15'

oe.o Into cock or the eequiee. pion ..pth, .h'cheve'" COM" fI.st.

D,)roe delven post, co.. drill . 4'Olone"r ho.. :8' d...p 'nto cock oe the eequire. pion oepth, whlch.ver co"e.. ri.st. e,) Fo. Anchor post, r.ontlnue diQglng24' .'o"etee, 30' d...p 1",0 rock oe the eequir.. pl.n ..eo'th, whichever cones fiest

a The Colbroltoe coble bocci.. syst." ,hu" be Inston.. 'n NCHRP

Repoet 350 stondor" co"",octed solt. Son nus.t b. ..t, d.oln...

9. Every conponent to be gotvonl.ed.

Allowo.ble Devlntlcn

frOM Cho.rt +/- !Or.

,

GIBRAL TAR C ~ . S ' 320 So"'thtond Rood able orner ystern [

D",rn.t, Texos 78611 : )-800"49:1'''8951 ~ I Pote"t p.rdi"~

DATE. )0/231D7 ;

Deflection jPost Spo,cina

9'3' 30.n

':I' "'".

8' ! 20.F'T

7' l?F

6'S' 1Of!.. ..........