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Safety Eligibility Letter B-150B

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U.S. Department of Transportation
Federal Highway Administration

1200 New Jersey Ave. S.E.
Washington, D.C. 20590

July 16, 2008

In Reply Refer To: HSSD/B-150B

Mr. Andrew Artar
Vice President Sales and Marketing
Gregory Highway Products
4100 13th Street, SW
Canton, OH  44710

Dear Mr. Artar:

This letter is in response to your request for Federal Highway Administration (FHWA) acceptance of a roadside safety system for use on the National Highway System (NHS).

Name of systems:Gregory Mini Spacer (GMS) Guardrail with 12’6” Post Spacing
GMS Median Barrier with 12’6” Post Spacing
Type of systems:Steel W-Beam Barriers
Test Level:The National Cooperation Highway Research Program (NCHRP)
Report 350 Test Level 3 (TL-3)
Testing conducted by:Southwest Research Institute
Date of request:March 22, 2008
Date of follow up:April 28, 2008

You requested that we find these systems acceptable for use on the NHS under the provisions of the proposed American Association of State Highway and Transportation Officials’ Manual for Assessing Safety Hardware-2008 (MASH-08).

Roadside safety systems should meet the guidelines contained in the NCHRP Report 350, "Recommended Procedures for the Safety Performance Evaluation of Highway Features". The FHWA Memorandum “ACTION: Identifying Acceptable Highway Safety Features” of July 25, 1997, provides further guidance on crash testing requirements of longitudinal barriers. However, in this case you have chosen to anticipate the adoption of MASH-08, an option that the FHWA has offered with the understanding that additional testing may need to be done if changes to the test criteria are made before MASH-08 is formally adopted.

The test article was a Modified G4(1S) longitudinal barrier. The length-of-need section consisted of standard unmodified 12-ga W-beam mounted directly to standard unmodified 6 foot long W6 x 8.5 steel posts using the proprietary GMS releasable fasteners. There were no blockouts or backup plates at any of the posts. All guardrail splices were located at the posts.

The posts were embedded to a depth of 44 inches and spaced at 12.5 feet. The Guardrail panels were each 12.5 feet long and mounted such that the top-of-rail height was 27-5/8 inches. The 187-foot long test section was adequately anchored at both ends.

Crash Testing
The Gregory Mini Spacer W-Beam Barrier (GMS-WB) was subjected to MASH-08 Test 3-11 using the 5000-pound quad-cab pickup truck. The test data summary sheet is enclosed for reference. Upon impact the barrier deflected 5.0 feet and the vehicle remained upright and in contact with the barrier a total of 46.8 feet. All occupant risk values were within acceptable limits.

Test 3-10 using the 1100C vehicle was waived because the small passenger car has been shown to have insufficient energy to cause significant horizontal deflection or vertical movement in the rail, and that there is little likelihood that it could under-ride the barrier.

You also requested the following variations to be accepted under MASH-08:

  2000P 2270P
Post Spacing Dynamic Deflection* Dynamic Deflection**
12 ft 6 in 5 ft 6 in 5 ft 10 in
6 ft 3 in 4 ft 1 in 4 ft 6 in
3 ft 1.5 in 3 ft 8 in 3 ft 11 in

*Maximum dynamic deflection. The NCHRP Report 350 criteria sets the “design deflection distance” at the maximum dynamic deflection recorded in Report 350 test 3-11. From the crash testing that you performed and your analysis (a method that agrees with a tuned Barrier VII analysis), you came up with recommended Report 350 test 3-11 (2000P) deflection criteria. You recommend that the minimum distances at which the face of a GMS installation be placed from the face of a rigid obstacle (e.g. bridge pier or overhead sign support) be 1.68m (5 ft 6 in), 1.25m (4 ft 1 in), and 1.12m (3 ft 8 in) for 12’6” (2x), standard 6’3” (1x), 3’ 1-1/2” (1/2 x) post spacing, respectively.

**Maximum dynamic deflection. Similarly, for test 3-11 (2270P) as the deflection criteria you recommend that the minimum distances at which the face of a GMS installation be placed from the face of a rigid obstacle (e.g. bridge pier or overhead sign support) be 1.78m (5 ft 10 in), 1.37m (4 ft 6 in), and 1.19m (3 ft 11 in) for 12’6” (2x), standard 6’3” (1x), 3’ 1 ½” (1/2 x) post spacing, respectively.

These offsets are based on the “working width” deflections seen in the crash tests/analysis and include some degree of pickup truck penetration beyond the vertical plane of the barrier’s dynamic deflection. As with all traffic barriers, larger offset distances would be required to shield similar features from vehicles with higher centers of gravity, such as single-unit trucks or busses, because of the relatively high roll angles seen with these vehicles in rigid and semi-rigid barrier tests of similar height.

Because the crash testing met the requirements of the proposed MASH-08 criteria, the system described above, as well as the variations 1 through 9, are acceptable for use on the NHS under the range of conditions tested, when such use is acceptable to a transportation agency.

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


Sincerely yours,

David A. Nicol

David A. Nicol, P.E.
Director, Office of Safety Design
Office of Safety


Table 4.1- Summary of Test Results and Conditions
Images of truck crashing into guardreail
General Information
Test AgencySouthwest Research Institute
Test NumberGMS-7
Test Date10/30/2007
Test Category3/11
Test Article
TypeLongitudinal Barrier
Installation Length57.15 m (187.5 ft)
Top-of-Rail Height702 mm (27 5/8 in)
Post Spacing3.81 m (12.5 ft)
Type of Primary BarrierModified G4(1S)
SoilStable, Dry-“Standard” Soil
Test Vehicle
Type½ Ton Quad Cab Pickup
Model2003 Dodge Ram 1500 Quad cab
Mass (kg)2241
Inertial Mass (kg)2241
Dummy Mass (kg)NA
Gross Static Mass (kg)2241
Impact Conditions
Speed (km/hr)102.3
Angle (degrees)23.9
Exit Conditions
Speed (km/hr)60 (calculated)
Angle (degrees)18
Occupant Risk Values
Impact Velocity (m/s)
Ridedown Accelerations (g's)
Test Article Deflection
Dynamic1.52 m (5.0 ft)
Max. Velhicle Intrusion1.80 m (5.92 ft)
Permanent0.53 m (1.75 ft)
Vehicle Damage
Max. Deform (mm)0
Post Impact Vehicle Behavior (limited to events <2.000 seconds)
Maximum Roll Angle (degrees)-28.3 @ 0.913 sec.
Maximum Pitch Angle (degrees)-12.9 @ 1.224 sec.
Maximum Yaw Angle (degrees)54.8 @ 1.190 sec.
Graph of truck crashing into guardreail
Page last modified on August 16, 2011.
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