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FHWA Home / Safety / Roadway Departure / Safety Eligibility Letter SS-163

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U.S. Department of Transportation
Federal Highway Administration

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

April 2, 2010

In Reply Refer To: HSSD/SS-163

Mr. Gary ODell, President
Information Display Company
10950 SW 5th Street, Suite 330
Beaverton, OR 97005

Dear Mr. ODell:

Thank you for your letter of September 14, 2009, requesting the Federal Highway Administration’s (FHWA) acceptance of your company’s Speed Check models VSC-1520 and VSC-1820 radar speed displays mounted to a breakaway pole as a crashworthy sign support system for use on the National Highway System (NHS). Accompanying your letter was an engineering analysis report that included calculations verifying the display connection strength, reference to previous crash tests of similar devices, and drawings of the system. You requested that we find the Speed Check systems 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 Speed Check VSC-1520, is a radar speed display with 15 inch digit height, and the VSC-1820 has a display with 18 inch digit height. The VSC-1520 weighs 51 pounds and the VSC-1820 weighs 62 pounds. The models are described in further detail in the enclosed engineering analysis report. Each radar speed display is attached to a 4-inch diameter pole and the bottom of the unit is mounted at least 84 inches from the ground using a minimum of 3/8-inch diameter U bolts made of A307 steel as shown in the enclosed report.

You referenced FHWA Acceptance Letters, SS-84, dated July 26, 1999, and SS-121, dated December 30, 2003, in which motorist aid call boxes were tested on poles mounted on 4-bolt slip bases. The call boxes were of weights slightly heavier than the Speed Check devices but mounted closer to the ground, near windshield height. In these test programs the occupant impact speeds and decelerations were well within limits, as was occupant compartment deformation (roof crush). However, in SS-84 the call boxes were mounted on the side of the support post and in SS-121 they were located on the backside of the post. The Speed Check sign units will be mounted on the post facing oncoming traffic and are therefore more likely to break free from the support post upon impact. The enclosed report with calculations shows the strength of the bolts is adequate to absorb the anticipated impact.

Based on the results of your calculations and the previous testing referenced above, the Speed Check installations are comparable and likely to meet the breakaway criteria under the NCHRP Report 350. Therefore, the devices described above and shown in the enclosed drawings for reference are acceptable for use as test level 3 devices on the NHS under the range of conditions tested, when proposed by a State. This acceptance will be limited to a generic four-bolt slip base or a comparable breakaway base using crashworthy, frangible couplings or frangible bases.

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


Sincerely yours,

/* Signature of David A. Nicol */

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


Page last modified on December 17, 2013.
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