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FHWA Home / Safety / Roadway Departure / Safety Eligibility Letter

Safety Eligibility Letter B-220

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U.S. Department of Transportation
Federal Highway Administration

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

May 3, 2011

In Reply Refer To:
HSST/B-220

Mr. John Addy
Hill & Smith. Inc.
Springvale Business and Industrial Park
Bilston, Wolverhampton, West Midlands, UK, WV14 OQL

Dear Mr. Addy:

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 system: Zoneguard™, Portable Steel Barrier Expansion Joint Units
Type of system: portable longitudinal steel barrier
Test Level: NCHRP Report 350 (Report 350) Test Level 3 (TL-3)
Testing conducted by: TRL Limited
Date of request: December 7, 2010
Date of follow-up: December 8, 2010
Task Force 13 Designator: SWM10

You requested that we find this system acceptable for use on the NHS under the provisions of National Cooperative Highway Research Program (NCHRP) Report 350 “Recommended Procedures for the Safety Performance Evaluation of Highway Features” for both the standard and minimum deflection arrangements of Zoneguard™.

Requirements
Roadside safety systems should meet the guidelines contained in the NCHRP Report 350, "Recommended Procedures for the Safety Performance Evaluation of Highway Features". FHWA Memorandum “ACTION: Identifying Acceptable Highway Safety Features” of July 25, 1997 provides further guidance on crash testing requirements of longitudinal barriers.

Decision
The following devices are found acceptable, with details provided below:

Description
The Zoneguard™, Portable Steel Barrier Expansion Joint Unit is an appurtenance to the previously accepted Zoneguard™ portable longitudinal barrier system as per FHWA acceptance letter HSSD/B-176 (as per Report 350). The test article description is as follows and in addition to the originally tested barrier as per HSSD/B-176.

The as tested barrier consisted of eight 12 meter (39.37 feet) ‘speed joint’ barriers. Each 12 meter (39.37 feet) length of barrier consisted of three 4 meter (13.12 feet) sections that were bolted together. The 4 meter (13.12 feet) section at impact point was a three part expansion joint with longitudinal expansion provided by eight sleeved tubes. Each of the expansion joint inner tubes measured 694 millimeters (27.32 inches) x 70 millimeters (2.75 inches) and passed through an outer sleeve (276 millimeters (10.86 inches) x 80 millimeters (3.15 inches)). Each inner tube was fitted with an end cap.

The approach side of the expansion joint was pinned on the traffic side at 29 meters (95.14 feet) and on the rear at 30 meters (98.42 feet), to the running surface using two 30 millimeter (1.18 inches) diameter 500 millimeter (19.68 inches) long pins. The base of each 12 meter (39.37 feet) barrier section had twelve rubber feet fitted that were fixed using contact adhesive. Some of these rubber feet were displaced from their original location. Due to variations in test site levels, not all of the feet were in contact with the ground; the foot at impact point was lifted off the running surface by 5 millimeters (0.197 inches) and barrier section number 4 was lifted off of the test surface by a nominal 20 millimeters (0.79 inches). The complete barrier installation was nominally 0.815 meters (2.67 feet) high, 0.7 meters (2.3 feet) wide and 96 meters (315 feet) long. The approach terminal was pinned using four 30 millimeter (1.18 inches) diameter 450 millimeter (17.72 inches) long terminal pins located at 0.45 meters (1.47 feet) and 4.45 meters (14.6 feet) measured from the start of the barrier. The departure terminal was pinned using four 30 millimeter (1.18 inches) diameter 500 millimeter (19.68 inches) long terminal pins located at 0.45 meters (17.72 inches) and 4.45 meters (14.6 feet) measured from the end of the barrier. The barrier was installed so that the vehicles center line intersected the barrier at a point 32.67 meters (107.19 feet) from the start of the barrier, with the point of first contact being 31.08 meters (102 feet) (0.92 meter (3 feet) before the end of the expansion joint barrier). To aid post test analysis two lines were painted behind the barrier at 1.7 meters (5.6 feet) and 2.7 meters (8.86 feet) measured from the front edge of the impact side of the barrier.

Details of this system are provided as enclosures to this correspondence.

Crash Testing
The barrier was crash tested at the test facilities at TRL Limited, United Kingdom according to the following testing criteria for the evaluation of temporary longitudinal barriers used in work and construction zones. This report describes the dynamic impact test of a Zoneguard™, Portable Steel Barrier fitted with Zoneguard™, Portable Steel Barrier Expansion Joint Unit to test designation level 3-11 as per NCHRP Report 350. The impact conditions of this test are met with a total test mass of 2,000 kg (4.4 kips) at a speed of 100 (± 4 %) km/h (62.13 mph) and at an angle of 25 (± 1.5) degrees to the line of the barrier traffic face. The impact speed was 100.6 km/h (62.5 mph) and the impact angle was 24.9 degrees and therefore satisfactory. However the vehicle’s actual total test mass was 2,139 kg (4.715 kips), which is outside the recommended value specified in Report 350 and therefore this test was not fully compliant with the requirements of Report 350. However this non compliance represents a worst case test in terms of test item performance. The dynamic deflection was 0.97 meter (3.18 feet) and the working width was 1.64 meters (5.38 feet). The permanent deflection was 0.82 meter (2.69 feet).

Analysis of the high speed footage, together with witness marks on the barrier, show that the right hand side of the vehicle remained in contact until the end of barrier number 4. After this point only the vehicle’s right-hand side wheel track remained in contact with the toe of the barrier. The vehicle continued on this path, travelling parallel to, and on the toe of the barrier. Once past the end of the departure terminal, the vehicle’s remotely operated brakes were applied and the vehicle came to a rest 34 meters (111.5 feet) beyond the end of, and 3 meters (9.84 feet) behind the barrier.

Findings
The analysis of the Report 350 TL3 testing showed there were no detached elements from the impacting vehicle or system that penetrated the occupant compartment of the impacting vehicle or presented hazards to others in the area. There was no significant deformation of the roof, windshield or occupant compartment. The occupant impact velocities and ridedown accelerations were within the recommended limits for the impacting vehicle.

Therefore, the system described in the request above and detailed in the enclosed drawings is acceptable for use on the NHS under the range of conditions tested, when such use is acceptable to a highway agency.

The Crash Test Summary details of this system are provided as enclosures to this correspondence.

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

 

Sincerely yours,

/* Signature of Michael S. Griffith */

Michael S. Griffith
Director, Office of Safety Technologies
Office of Safety

Enclosures

Page last modified on June 24, 2011.
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