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Interpretation Letter 4(09)-001(I) - Covering Signals Out of Service

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U.S. Department of Transportation
Federal Highway Administration

1200 New Jersey Avenue, SE.
Washington, D.C. 20590

February 22, 2010

In Reply Refer To: HOTO-1

Mr. John Tatum
Traffic Engineer
City of Marysville
80 Columbia Avenue
Marysville, WA 98270

Dear Mr. Tatum:

Thank you for your February 2 e-mail to Mr. Scott Wainwright of our Manual on Uniform Traffic Control Devices (MUTCD) Team requesting an interpretation of Section 4D.01 of the 2009 edition of the MUTCD in regard to covering of signal faces that are out of service when such signal faces have backplates with yellow retroreflective borders.

The 2009 edition of the MUTCD contains new provisions that allow the use of a retroreflective yellow border on the perimeter of signal face backplates for enhanced nighttime conspicuity. During a temporary power failure that causes the signals to be "dark," the retroreflective backplate border also helps road users to recognize the presence of a signalized intersection and react appropriately, such as treating the intersection as an all-way stop, as is required by law in some States.

However, such laws are not intended to apply to new signal faces that have been purposely installed prior to being placed into service or during scheduled seasonal shutdowns of the traffic control signal operation at an intersection. Paragraph 03 of Section 4D.01 is this Standard statement, which is intended to apply to this condition:

"When a traffic control signal is not in operation, such as before it is placed in service, during seasonal shutdowns, or when it is not desirable to operate the traffic control signal, the signal faces shall be covered, turned, or taken down to clearly indicate that the traffic control signal is not in operation."

The intent of this paragraph in Section 4D.01 is to avoid misleading unfamiliar road users into thinking that the intersection is signalized but the power has failed, because that could cause some road users to unexpectedly come to a stop, when no such stop is required by the right-of-way controls that are in place at the intersection.

When signal faces have been installed at a location prior to being placed into service, or when a traffic control signal is in a seasonal shutdown, it is inappropriate for the yellow retroreflective backplate border, if used, to be visible. Merely covering the signal sections themselves and leaving the yellow-bordered backplate uncovered is not sufficient to "clearly indicate that the signal is not in operation," especially during nighttime conditions.

Therefore, it is our official interpretation of Section 4D.01, paragraph 03, that if the signal faces have backplates with yellow borders, the entire faces, including the backplates, should be covered. Additionally, if the signal faces are turned, rather than covered, they should be oriented such that the yellow backplate borders will not reflect light back to road users on any of the approaches to the intersection.

Thank you for writing on this subject. We hope that this interpretation answers your question. If you have any questions, please contact Mr. Wainwright by e-mail at or by telephone at 202 366 0857. Please note that we have assigned your request the following official interpretation number and title: "4(09)-001(I) - Covering Signals Out of Service." Please refer to this number in any future correspondence regarding this issue.

Sincerely yours,

Original signed by:

Mark R. Kehrli
Director, Office of Transportation Operations

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