1200 New Jersey Ave., SE

 Washington, D.C. 20590

August 16, 2011

In Reply Refer To:

HSSD/CC-103A

Mr. Gerrit A. Dyke, P.E.

Vice President of Engineering and R & D

Barrier Systems, Inc.

3333 Vaca Valley Parkway, Suite 800

Vacaville, CA 95688

Dear Mr. Dyke:

This letter is in response to your request for the Federal Highway Administration (FHWA) 

acceptance of a modified trailer-mounted attenuator for use on the National Highway System (NHS).

Name of system: U-MAD Trailer-Mounted TMA

Type of system: Trailer-Mounted Attenuator

Test Level: NCHRP Report 350 TL-3 

Testing conducted by: not applicable

Date of request: December 30, 2010

Date received by FHWA: January 7, 2011

You requested that we find a modified version of your previously-accepted U-MAD trailer 

attenuator acceptable for use on the NHS under the provisions of the National Cooperative Highway 

Research Program (NCHRP) Report 350 “Recommended Procedures for the Safety Performance 

Evaluation of Highway Features.”

Requirements

Roadside safety devices should meet the guidelines contained in NCHRP Report 350 if tested 

prior to January 1, 2011, and the guidelines in AASHTO’s Manual for Assessing Safety 

Hardware if tested after that date. The FHWA memorandum “ACTION: Identifying Acceptable 

Highway Safety Features” of July 24, 1997, provides further guidance on crash testing 

requirements of longitudinal barriers and crash cushions. Modifications to previously-accepted 

devices that are not likely to affect crash performance may be accepted without additional crash 

testing.

Decision

The U-MAD trailer-mounted TMA was previously accepted as a TL-2/TL-3 design in FHWA 

acceptance letter CC-103. This design was modified by the addition of mounting brackets and a 

removable sign board assembly, as described below. Based on the results of your analysis, as 

summarized below, the FHWA agrees that your modified trailer-mounted attenuator remains a 

crashworthy design under NCHRP Report 350 at TL-2 and TL-3, depending on which energyabsorbing cartridge is mounted on the trailer.

FHWA: HSSI: WLongstreet: mb: x60087:7/15/11

File: h: //directory folder/HSST/ CC103A_U-MAD Trailer Mounted TMA.docx

cc: HSST Will Longstreet 
2

Description

The basic U-MAD trailer-mounted attenuator described in detail in FHWA acceptance letter CC103 was modified to add mounting brackets for a removable illuminated sign board assembly. 

Modifications to the trailer frame consist of two upright steel tubes and gussets welded to the 

trailer frame. The uprights are 3.5-inch x 2.5-inch x 3/16-inch (90-millimeter x 65-millimeter x 

5-millimeter) steel tubes and the gussets are 1.5-inch x 1.5-inch x 3/16-inch (40-millimeter x 40-

millimeter x 5-millimeter) steel angles. The sign support frame is made from 2-inch x 3-inch x 

3/16-inch (50-millimeter x 75-millimeter x 5-millimeter) steel structural tubing designed to 

accommodate a 4-foot x 8-foot (1.2-meter x 2.4-meter) sign board. Enclosure 1 shows the 

modified trailer and Enclosure 2 shows the trailer with a TL-3 U-MAD cartridge and a sign 

board in place.

Testing

The design of the U-MAD trailer-mounted attenuator is such that an impacting vehicle is not 

likely to contact the trailer assembly when it is loaded with a TL-2 or a TL-3 U-MAD cartridge. 

The weight of the sign board and mounting hardware increases the total weight of the unit by 

approximately 12 percent. Your conservation of momentum analysis concluded that this minor 

increase in weight would not cause a significant increase in the occupant impact velocity 

reported in test 3-51 for the un-modified design. Your structural analysis further concluded that 

the sign board mounting structure and hardware is sufficient to withstand the maximum loads 

associated with an NCHRP Report 350 TL-3 impact. We have reviewed your analysis and agree 

with your conclusions. 

Findings

Based on the considerations noted above, the FHWA agrees that the U-MAD trailer-mounted 

attenuator, as modified, remains acceptable as an NCHRP Report 350 TL-2 or TL-3 attenuator. 

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

• This acceptance letter provides an AASHTO/ARTBA/AGC Task Force 13 designator 

that should be used to identify any new or updated Task Force 13 drawings for this 

product.

• This acceptance is limited to the crashworthiness characteristics of the device and does 

not cover its structural features, nor conformity with the Manual on Uniform Traffic 

Control Devices.

• Any design 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, the 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 
3

acceptance, and that it will meet the crashworthiness requirements of NCHRP Report 

350.

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

CC-103A shall not be reproduced except in full. This letter, and 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 modified U-MAD trailer-mounted attenuator is a patented product and is considered 

proprietary. If proprietary devices are specified by a highway agency for use on Federalaid 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.

Sincerely yours,

Michael S. Griffith

Director, Office of Safety Technologies

Office of Safety

Enclosures
 1200 New Jersey Ave., SE

 Washington, D.C. 20590

August 16, 2011

In Reply Refer To:

HSSD/CC-103A

Mr. Gerrit A. Dyke, P.E.

Vice President of Engineering and R & D

Barrier Systems, Inc.

3333 Vaca Valley Parkway, Suite 800

Vacaville, CA 95688

Dear Mr. Dyke:

This letter is in response to your request for the Federal Highway Administration (FHWA) 

acceptance of a modified trailer-mounted attenuator for use on the National Highway System (NHS).

Name of system: U-MAD Trailer-Mounted TMA

Type of system: Trailer-Mounted Attenuator

Test Level: NCHRP Report 350 TL-3 

Testing conducted by: not applicable

Date of request: December 30, 2010

Date received by FHWA: January 7, 2011

You requested that we find a modified version of your previously-accepted U-MAD trailer 

attenuator acceptable for use on the NHS under the provisions of the National Cooperative Highway 

Research Program (NCHRP) Report 350 “Recommended Procedures for the Safety Performance 

Evaluation of Highway Features.”

Requirements

Roadside safety devices should meet the guidelines contained in NCHRP Report 350 if tested 

prior to January 1, 2011, and the guidelines in AASHTO’s Manual for Assessing Safety 

Hardware if tested after that date. The FHWA memorandum “ACTION: Identifying Acceptable 

Highway Safety Features” of July 24, 1997, provides further guidance on crash testing 

requirements of longitudinal barriers and crash cushions. Modifications to previously-accepted 

devices that are not likely to affect crash performance may be accepted without additional crash 

testing.

Decision

The U-MAD trailer-mounted TMA was previously accepted as a TL-2/TL-3 design in FHWA 

acceptance letter CC-103. This design was modified by the addition of mounting brackets and a 

removable sign board assembly, as described below. Based on the results of your analysis, as 

summarized below, the FHWA agrees that your modified trailer-mounted attenuator remains a 

crashworthy design under NCHRP Report 350 at TL-2 and TL-3, depending on which energyabsorbing cartridge is mounted on the trailer.
2

Description

The basic U-MAD trailer-mounted attenuator described in detail in FHWA acceptance letter CC103 was modified to add mounting brackets for a removable illuminated sign board assembly. 

Modifications to the trailer frame consist of two upright steel tubes and gussets welded to the 

trailer frame. The uprights are 3.5-inch x 2.5-inch x 3/16-inch (90-millimeter x 65-millimeter x 

5-millimeter) steel tubes and the gussets are 1.5-inch x 1.5-inch x 3/16-inch (40-millimeter x 40-

millimeter x 5-millimeter) steel angles. The sign support frame is made from 2-inch x 3-inch x 

3/16-inch (50-millimeter x 75-millimeter x 5-millimeter) steel structural tubing designed to 

accommodate a 4-foot x 8-foot (1.2-meter x 2.4-meter) sign board. Enclosure 1 shows the 

modified trailer and Enclosure 2 shows the trailer with a TL-3 U-MAD cartridge and a sign 

board in place.

Testing

The design of the U-MAD trailer-mounted attenuator is such that an impacting vehicle is not 

likely to contact the trailer assembly when it is loaded with a TL-2 or a TL-3 U-MAD cartridge. 

The weight of the sign board and mounting hardware increases the total weight of the unit by 

approximately 12 percent. Your conservation of momentum analysis concluded that this minor 

increase in weight would not cause a significant increase in the occupant impact velocity 

reported in test 3-51 for the un-modified design. Your structural analysis further concluded that 

the sign board mounting structure and hardware is sufficient to withstand the maximum loads 

associated with an NCHRP Report 350 TL-3 impact. We have reviewed your analysis and agree 

with your conclusions. 

Findings

Based on the considerations noted above, the FHWA agrees that the U-MAD trailer-mounted 

attenuator, as modified, remains acceptable as an NCHRP Report 350 TL-2 or TL-3 attenuator. 

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

• This acceptance letter provides an AASHTO/ARTBA/AGC Task Force 13 designator 

that should be used to identify any new or updated Task Force 13 drawings for this 

product.

• This acceptance is limited to the crashworthiness characteristics of the device and does 

not cover its structural features, nor conformity with the Manual on Uniform Traffic 

Control Devices.

• Any design 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, the 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 
3

acceptance, and that it will meet the crashworthiness requirements of NCHRP Report 

350.

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

CC-103A shall not be reproduced except in full. This letter, and 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 modified U-MAD trailer-mounted attenuator is a patented product and is considered 

proprietary. If proprietary devices are specified by a highway agency for use on Federalaid 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.

Sincerely yours,

Michael S. Griffith

Director, Office of Safety Technologies

Office of Safety

Enclosures