Subject:  INFORMATION:  Cable Barrier Transitions to W­Beam 

Guardrail

/original signed by/

From:  John R. Baxter 

Director, Office of Safety Design 

To:  Director of Field Services

Resource Center Managers

Division Administrators

Safety Field 

In the late 1980’s, the Southwest Research Institute conducted successful crash tests on a cable 

barrier transition to a strong­post W­beam guardrail using a passenger sedan. In 1998, the 

Midwest Roadside Safety Facility (MwRSF) tested this transition design using NCHRP Report 

350 test vehicles and concluded that it met all appropriate evaluation criteria at test level 3 

(TL­3). The non­proprietary design tested in both cases was one developed by the South Dakota 

Department of Transportation. This design transitioned the generic 3­strand cable barrier over 

and under the W­beam using special steel straps and connected each cable to a standard concrete 

anchor block located behind the W­beam. A reduced post spacing was used as the cable barrier 

approached the W­beam installation, which was itself anchored with a Breakaway Cable 

Terminal (BCT) offset 4 feet from the cable barrier. In 2002, the MwRSF again tested this

design successfully with the 2000­kg pickup truck, but with a FLEAT guardrail terminal 

anchoring the W­beam installation in lieu of a BCT. Although the South Dakota design remains

an acceptable TL­3 transition, the 6­foot or more dynamic deflection of the cable barrier in each 

of the Report 350 crash tests allowed direct vehicular contact with the W­beam terminals,

resulting in considerable pitch, yaw, and roll to the pickup trucks. This design also requires

installation of a downstream anchor for the cable barrier.

Recently, the manufacturers of several of the high­tensioned proprietary cable barrier systems

have requested acceptance of unique transition designs for connecting their barriers to strongpost W­beam and/or Thrie­beam guardrail. Each of these eliminates the need for a separate 

downstream cable anchor by attaching each cable directly to the metal beam rail element. Like 

the South Dakota design, the cable rail post spacing is also reduced to further limit deflection of

the cable in the transition area.  Reduced dynamic deflection can also be expected with the 

greater cable tension specified for all of the proprietary designs.

Memorandum

Date:  May 8, 2006 

Reply to 

Attn. of:  HSA­10/B147
2 

Each of these designs has been previously accepted as a TL­3 transition based on our review of

the designs themselves and the crash testing done on the South Dakota design. Copies of the 

letters sent to each manufacturer are attached for ready reference. Note that for each specific 

design, the W­beam terminal itself should be offset at least 4 feet. Because the cable will 

prevent virtually all head­on impacts into the W­beam terminal, a light­weight, non­energy 

absorbing terminal would be the preferred method of anchoring the W­beam barrier. The 

MELT, which has been accepted as a TL­2 design, could be used to anchor the W­beam if a 

generic terminal is desired. 

Attachments
June 8, 2004 

Mr. Rodney A. Boyd 

Trinity Highway Safety Products Division 

P.O. Box 568887 

Dallas, Texas 75356­8887 

Dear Mr. Boyd: 

In his May 12 letter to Mr. Richard Powers of my staff, Mr. Brian Smith requested formal 

Federal Highway Administration acceptance of a design by which your CASS cable barrier is

transitioned to a strong­post W­beam or Thrie­beam guardrail.

The CASS to W­Beam Transition and CASS to Thrie Beam Transition were submitted for

acceptance for use in front of standard W­beam terminals having a 4’0” minimum offset 

behind the 3­cable prestretched and tensioned CASS system. The transition includes 10­gauge

W­beam (either two 12’6”­long or one 25’­long element) or 10­gauge Thrie beam rail elements

(one 12’6”­long element and one 6’3”­long transition element) with one­inch wide by 12­inch 

long slots in the valley of the rail elements. The cables are threaded through the front of the 

rail and connected to standard cable anchor brackets bolted to the backside of the rail elements. The first CASS post is placed 12’0” from the point where the cables first meet the W­beam or

Thrie beam. The transition then consists of 14 CASS posts spaced at 5’0” on center, and then 

5 posts spaced on 10’0” centers. The 3 cables, starting at the second post or 17’0” from the 

tangent W­beam or Thrie beam, taper together to nest into the valley(s) of the W­beam or Thrie 

beam. Design and layout details are shown in the enclosed drawings.

Previous full­scale crash testing has shown that the high tension and pre­stretched cables of the 

CASS system result in lower deflections than those seen in the non­tensioned cable barrier. In 

earlier cable­to­W­beam transition testing with the lower­tensioned generic cable rail, the cable 

deflection allowed the W­beam terminals to be impacted, resulting in some vehicle instability. With the CASS Transition, it is less likely that the nose of the terminal will be impacted in a 

typical design impact.

Based on the specific design details noted above, the CASS to W­Beam or Thrie Beam 

Transitions may be considered acceptable for use on the National Highway System at National 

Cooperative Highway Research Program Report 350 test level 3 when used in conjunction with 

400 Seventh St., S.W. Washington, D.C. 20590

In Reply Refer To: HSA­10
2 

any crashworthy terminal having a minimum 4­foot offset from the cables. Since this design 

has not been physically tested, field installations should be monitored to verify both its ease of

construction and its presumed crashworthiness.

Sincerely yours,

/Original Signed by Richard D. Powers/ ~for~

John R. Baxter, P.E.

Director, Office of Safety Design 

Office of Safety 

Enclosures
PLAN VIEW ~ CASS - SRT CONNECTION

(W-BEAM GUARDRAIL WITH 8-POST SRT)

VIEW A-A

SECTION D-D SECTION C-C SECTION B-B

44

55

66

77

88

A B C D 

A A

DD

CC

B

B

(2) 12'-6" CABLE ANCHOR W-BEAM SECTIONS AT 12'-6" = 25'-0" 12'-0" (14) POST SPACES AT 5'-0" = 70' 

6

'

-

0

"

M

N

I

.

12'-0" 

(4) SPACES AT 6'-3" = 25'-0"

CABLE ANCHORBOTTOM CABLE

CABLE ANCHORTOP CABLE

CABLE ANCHORMIDDLE CABLE

1

'

-

9

"

12'-6"

12'-6"

6'-3" 6'-3" 6'-3"

12'-6"

6'-3"

6'-3"

6'-3"

4'-2" 4'-2"

4'-2" 4'-2"

37'-6" SRT

1

15

(3) CASS CABLES(TOP, MIDDLE &BOTTOM CABLE)

(2) CASS CABLES(MIDDLE & BOTTOMCABLE)

(1) CASS CABLE(BOTTOM CABLE)
PLAN VIEW ~ CASS - SRT CONNECTION

(THRIEBEAM GUARDRAIL WITH 8-POST SRT)

VIEW A-A

SECTION C-C SECTION B-B

44

55

66

77

88

A B C D 

A A

CC

BB

CABLE ANCHOR(MIDDLE CABLE)

1

15

(4) POST SPACES AT 6'-3" = 25'

CABLE ANCHOR(TOP & BOTTOMCABLE)

6'-3"

6'-3"

5

'

-

6

"M

N

I

.

6'-3" 6'-3" 6'-3"

12'-6" THRIEBEAM 12'-6" CABLE ANCHOR SECTION

THRIEBEAM TO W-BEAMTRANSITION

12'-0" (14) CASS POST SPACING AT 5'-0" = 70' 

1

'

-

9

"

12' 

(2) CASS CABLES(TOP & MIDDLE CABLE)

(1) CASS CABLE(BOTTOM CABLE)

4'-2" 4'-2"

12'-6"

(1) CASS CABLE(MIDDLE CABLE)

CABLE ANCHOR(TOP CABLE)

CABLE ANCHOR(BOTTOM CABLE)

CABLE ANCHOR(MIDDLE CABLE)

THRIEBEAM TO W-BEAMGUARDRAIL TRANSITION

12'-6"

4'-2" 4'-2"

37'-6" SRT

6'-3"
PLAN VIEW ~ CASS - SRT CONNECTION

(W-BEAM GUARDRAIL WITH 6-POST SRT)

VIEW A-A

SECTION D-D SECTION C-C SECTION B-B

44

55

66

77

88

A B C D 

A A

DD C

C

B

B

CABLE ANCHORBOTTOM CABLE

CABLE ANCHORTOP CABLE

CABLE ANCHORMIDDLE CABLE

1

9

(3) CASS CABLES(TOP, MIDDLE &BOTTOM CABLE)

(2) CASS CABLES(MIDDLE & BOTTOMCABLE)

(1) CASS CABLE(BOTTOM CABLE)

6'-3" 6'-3" 6'-3"

(14) POST SPACES AT 5'-0" = 70' 

1

'

-

9

"

4

'

-

0

"M

IN

.

12'-6"

6'-3"

6'-3" 6'-3"

12'-0" (2) 12'-6" CABLE ANCHOR W-BEAM SECTION AT 12'-6" = 25'-0"

6'-3"

12'-6"

37'-6" ( 6-POST SRT )

12' (4) POST SPACES AT 6'-3" = 25'
SECTION A-A

11

22

A 

B 

PROJ.

TRINITY INDUSTRIES, INCHIGHWAY SAFETY DIVISION

CASS - WBEAM

CASS TO W-BEAM 

GUARD RAIL CONNECTIO

10/12'6/6'3/CASS-CA/S

1 1 10 GA W-BEAM 12'-6" 

BILL OF MATERIAL

QTY ITEM DESCRIPTION LENGTH L

AA

4 1/4"

(3) AT 4" = 1'

6'-3" 6'-3"

1'-2"

1' 1'-7 1/2" 1' 

6 1/4"

8 1/2" 

n1 3/8"

n1" n1"

n1 3/8"

29/32" x 1 1/8"(8) SLOTS

29/32" x 1 1/8"(8) SLOTS

12'-6" 

3/4" x 2 1/2"(3 SLOTS)

n3/4" (8)

HOLES

n3/4" (8)

HOLES(2 PLC'S)

1'-2" (3) AT 4" = 1'

13'-6 1/2"

SLOT SLOT
SECTION A-A

22

33

44

A 

B 

PROJ.

CASS - THRIEBEAM

1 1 033922 10 G

QTY ITEM PC NO. 

AA

13'-6 1/2"

6'-3" 

6 1/4"

1'-2" (3) AT 4" = 1' 1'-2" (3) A

1' SLOT 1'-7 1/2" 

1

n3/4" (16)

HOLES

8 1/2"

4 1/4" 

29/32" x 1 1/8"(12) SLOTS

n3/4" (16)

HOLES

n1 3/8"

TYP.

n1"

TYP.

n3/4" x 2 1/2"

(6) SLOTS

12'-6" 
 

400 Seventh St., S.W. 

Washington, D.C. 20590

October 4, 2005 

In Reply Refer To: HSA-10

 Mr. Jerry Emerson, P.E. 

 BrifenUSA, Inc. 

 P.O. Box 94220 

 Oklahoma City, Oklahoma 73143 

 

 Dear Mr. Emerson: 

In your September 2 letter to Mr. Richard Powers of my staff, you requested formal Federal 

Highway Administration acceptance of a design concept by which your Brifen Wire Rope 

Safety Fence (WRSF) could be transitioned and connected to a strong-post W-beam or 

Thrie-beam guardrail. 

The Brifen WRSF to W-Beam Transition was submitted for acceptance for use in front of 

standard W-beam terminals having a 4’-0” minimum offset behind the 4-cable pre-stretched 

and tensioned Brifen system. The 4-cable transition requires four 12-gauge W-beam rail 

elements 12’-6” long, beginning at the first standard line post in the barrier installation. A 

unique Brifen attachment bracket is bolted to the rail at each of the first four W-beam rail 

splice locations and one cable is anchored at each of these brackets. For your 3-cable WRSF, 

three 12.5’ W-beam rail elements and attachment brackets are used. The first WRSF post is 

placed 10.5’ upstream from the first standard guardrail line post at which the lowest cable is 

connected to the W-beam. The upstream WRSF transition then consists of 16 additional line 

posts set on 5.25’ centers, at which point the standard WRSF post spacing (10.5’ or other) 

begins. Details for the 4-cable, 10.5’ post spacing WRSF transition are shown in the enclosed 

drawing. 

Attachment to Thrie-beam guardrail is similar to that shown for W-beam except that, for your 

4-cable system, two attachment brackets are located at the first splice and two are located at the 

second splice. The top and second cables are connected to the brackets in the upper valley (top 

cable at second splice) and the third and bottom cables are attached to the brackets in the lower 

valley (bottom cable at first splice). For your 3-cable WRSF the top two cables are attached to 

the two upper valley brackets (top cable at second splice) and the bottom cable is attached in 

the lower valley at the first splice location. As with W-beam, all attachments must be at a 

splice. 

 
2

Previous full-scale crash testing has shown that the high tension and pre-stretched cables of the 

Brifen WRSF result in lower deflections than those seen in the lesser-tensioned generic cable 

barrier. In earlier cable-to-W-beam transition testing with the lower-tensioned generic cable 

rail, the cable deflection allowed the W-beam terminals to be impacted, resulting in significant 

vehicle instability. With the Brifen WRSF design, it is less likely that the nose of the terminal 

will be impacted in a typical design impact. Even so, the use of a lightweight, non-energy 

absorbing W-beam terminal is suggested to minimize vehicle instability if the terminal is hit. 

Based on the specific design details noted above, the Brifen WRSF to W-Beam or Thrie Beam 

Transitions may be considered acceptable for use on the National Highway System at National 

Cooperative Highway Research Program Report 350 test level 3 when used in conjunction with 

a crashworthy terminal having a minimum 4-foot offset from the cables. The design may also 

be used to connect the WRSF to a weak post W-beam installation when the W-beam is 

adequately anchored with a crashworthy terminal. Since these transition designs have not been 

physically tested, field installations should be monitored to verify their presumed 

crashworthiness.

Sincerely yours, 

 

/original signed by/ 

John R. Baxter, P.E. 

 Director, Office of Safety Design 

Office of Safety 

Enclosure 

 

400 Seventh St., S.W. 

Washington, D.C. 20590

October 19, 2005 

In Reply Refer To: HSA-10

 

 

 Mr. Rick Mauer 

 Outside Sales National Representative 

 Nucor Steel Marion, Inc. 

 912 Chaney Avenue 

 Marion, Ohio 43302 

Dear Mr. Mauer: 

In your September 2 letter to Mr. Richard Powers of my staff, you requested formal Federal 

Highway Administration acceptance of a design concept by which your high-tension cable rail 

could be transitioned and connected to a strong-post W-beam guardrail. 

Your transition design is intended for use in conjunction with a W-beam installation that has a 

standard, crashworthy terminal with a minimum 4’-0” offset from the cable. A unique gusset 

plate is nested behind and bolted to the back of a special 6 foot-3 inch W-beam panel at the 

splice located at the first line post. Each cable is threaded through 1-in by 2-in slots in the 

W-beam panel and connected to the bracket. The first U-channel cable post is placed in line 

with the barrier proper and 6.5 feet upstream from the first W-beam line post. The transition 

then consists of 11 additional line posts also set on 6.5 foot centers, at which point your 

standard post spacing begins. Details for the transition design are shown in the enclosed 

drawings. 

Previous full-scale crash testing has shown that high-tension cable barriers result in lower 

deflections than those seen in the lesser-tensioned generic cable barrier. In earlier 

cable-to-W-beam transition testing with the lower-tensioned generic cable rail, the cable 

deflection allowed the W-beam terminals to be impacted, resulting in significant vehicle 

instability. With your high-tension design, it is less likely that the nose of the terminal will be 

impacted in a typical impact. Even so, the use of a lightweight, non-energy absorbing W-beam 

terminal is suggested to minimize vehicle instability if the terminal is hit. 

Based on the specific design details noted above, your proposed transition design is acceptable 

for use on the National Highway System at National Cooperative Highway Research Program 

Report 350 test level 3 when used in conjunction with a crashworthy terminal having a 

 
2

minimum 4-foot offset from the cables. Since this transition design has not been physically 

tested, field installations should be monitored to verify their presumed crashworthiness.

Sincerely yours, 

 

 /original signed by George Ed Rice, Jr./ 

 ~for~ 

John R. Baxter, P.E. 

 Director, Office of Safety Design 

 Office of Safety 

Enclosure