Refer to: HSA-10/WZ-131

Mr. Brian A. Brown
499 Carolina Street
San Francisco, California 94107

Dear Mr. Brown

Thank you for your letter of June 20, 2002, requesting Federal Highway Administration (FHWA) acceptance of the SonoBlaster work zone intrusion alarm as a crashworthy traffic control device for use on the National Highway System (NHS). Accompanying your letter was a report of crash testing conducted by the California Department of Transportation and a CD-ROM disc with a video of the tests. You requested that we find these devices 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.”


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 AINFORMATION: Crash Tested Work Zone Traffic Control Devices.” This later memorandum lists devices that are acceptable under Categories I, II, and III.

The SonoBlaster Work Zone Intrusion Alarm is portable safety alarm designed to be attached to cones, drums, or other channelizing devices to provide an audible warning to personnel in work zones. Weighing approximately 4 pounds, the lightweight unit is powered by CO2 cartridges and is activated by shock, impact, or tilt.


Because of the unique nature of the SonoBlaster you contacted us to discuss what testing would demonstrate the crashworthiness of the device. As it is an attachment to be used with cones or drums, it is considered to be a Category II work zone traffic control device eligible for reduced testing/reporting procedures than those normally required by NCHRP Report 350. Due to the very small mass and the low placement of the device, we agreed that informal testing with any vehicle would be sufficient to demonstrate what effect the SonoBlaster attachment would have. A cone was chosen as the "worst case scenario” for this testing.

Two live-driver tests were run, each using a 28-inch tall traffic cone with the SonoBlaster attached. A Ford Excursion impacted the device at 45 mph and 60 mph. In both cases the device rolled underneath the vehicle. The cone and SonoBlaster caused no damage to the vehicle and showed no potential for occupant compartment intrusion. The vehicle's velocity was also unaffected.


The results of the testing met the FHWA requirements and, therefore, the SonoBlaster described above and shown in the enclosed drawings for reference are acceptable for use on the NHS under the range of conditions tested, when proposed by a State.

We consider the SonoBlaster to be acceptable when attached to the base of conventional traffic cones, plastic drums, or large base road tubes or delineators (i.e., the "Navigator" manufactured by Plastic Safety Systems).

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

Sincerely yours,

Carol H. Jacoby, P.E.

Director, Office of Safety Design