Federal Highway Administration
1200 New Jersey Ave. S.E.
Washington, D.C. 20590
February 8, 2008
In Reply Refer To: HSSD/WZ-267
Mr. David Krahulec
Vice President/Chief Operating Officer
Horizon Signal Technologies, Inc.
216 Line Road
Malvern, PA 19355
Dear Mr. Krahulec:
In your January 2, 2008, letter you requested the Federal Highway Administration’s (FHWA) acceptance of your company’s SQ2 pedestal mount portable traffic signal system as a crashworthy traffic control device for use in work zones on the National Highway System (NHS). Accompanying your letter was a crash test report prepared by Transportation Research Center Inc., videos of the crash test conducted, and a drawing of the SQ2 system. You requested that we find this device 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.”
The FHWA guidance on crash testing of work zone traffic control devices is contained in two memoranda. The first, dated July 25, 1997, titled “INFORMATION: Identifying Acceptable Highway Safety Features,” established four categories of work zone devices: Category I devices were those lightweight devices which could be self-certified by the vendor, Category II devices were other lightweight devices which needed individual crash testing, Category III devices were barriers and other fixed or massive devices also needing crash testing, and Category IV devices were trailer mounted lighted signs, arrow panels, etc. The second guidance memorandum was issued on August 28, 1998, and is titled “INFORMATION: Crash Tested Work Zone Traffic Control Devices.” This later memorandum lists devices that are acceptable under Categories I, II, and III.
The SQ2 pedestal mount portable traffic signal system consists of three signal lights mounted on a retractable, manually operated boom, powered by two 12-volt batteries. The signal heads are cast aluminum and have three 12-inch (30.5 cm) diameter LED signal lamps. The signal heads are equipped with visors that extend a minimum of 10 inches (25.4 cm) beyond the signal head. The total mass of the system is approximately 385.8 pounds (175 kg). The overall extended height of each SQ2 system is 11.33 feet (3.45 m) and its width is 27.5 inches (0.70 m). A detailed drawing of the SQ2 pedestal mount portable traffic signal system is enclosed.
In coordination with the FHWA you conducted a crash test (Test 3-71) to verify the impact performance of your device at an impact speed of 62 mph (99.8 km/h) using a 820C passenger car test vehicle. The crash test set up was such that the test vehicle impacted a pair of the SQ2 signal systems simultaneously. One of the signal systems was oriented with the signal head facing the test vehicle and another signal system was rotated 90 degrees with the signal head facing the first signal system. The FHWA recommended test setup protocol typically requires that the second device be rotated or oriented 90 degrees from the first system and placed 20 feet (6.1 m) downstream from the first device. The test set up protocol concerning downstream placementwas outside the recommendations but the FHWA does accept the results of the test as conducted and will not require a retest.
During the test, the vehicle bumper contacted the two signal systems simultaneously. Upon impact, the signal system supports rotated and both signal heads fully impacted the roof. The vehicle remained upright and maximum displacement of the signal systems was 273.3 feet (83.3 m) measured longitudinally from the point of impact. The maximum occupant compartment deformation was 2.67 inches (67 mm) at the passenger side of the roof. The maximum occupant impact velocity was 16.78 mph (7.5 m/s) and the maximum occupant ridedown acceleration was 2.9 g’s.
In summary, the SQ2 pedestal mount portable traffic signal system, as described above, meets the appropriate evaluation criteria for NCHRP 350 Test Level 3 work zone traffic control devices and may be used at all appropriate locations on the NHS when selected by the contracting authority. This device is accepted by the FHWA for use under the range of conditions tested and is considered crashworthy when deployed at the fully extended height of 11.33 feet (3.45 m).
Please note the following standard provisions that apply to the FHWA letters of acceptance:
David A. Nicol
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