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Interpretation Letter 6(09)-15 (I) — Clarification of Interpretation 6(09)-5

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U.S. Department of Transportation
Federal Highway Administration

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

September 19, 2012

In Reply Refer To: HOTO-1

Mr. Dennis Hilton
President and CEO
IntelliStrobe Safety Systems
3854 South Avenue
Springfield, Missouri 65807

Dear Mr. Hilton:

Thank you for your e-mail message dated July 20 requesting a clarification of Official Interpretation 6(09)-5, which we issued on August 31, 2010 regarding the combined use of pilot cars and temporary traffic control signals. Specifically, you requested the reasoning for mentioning the Automated Flagger Assistance Device (AFAD) in the third paragraph of the interpretation letter since the request concerned the use of temporary traffic control signals instead of flaggers, not AFADs instead of flaggers, and the mention of these devices in the third paragraph is creating an impression that AFADs and temporary traffic control signals are equivalent.

A pilot car is generally used to guide a queue of vehicles through a one-lane, two-way section of roadway in a temporary traffic control zone where the affected section is lengthy or the path is confusing to follow because of construction operations. This frequently results in long waiting times for road users and it is not always apparent why the delay is so long. During a large portion of this waiting time, no vehicles travelling in the oncoming direction are in view. This can give impatient drivers the impression that an automatic or unmanned device is not functioning properly and can result in a driver inappropriately entering the one-lane, two-way section in an unauthorized direction. That is why Paragraph 4 of Section 6C.13 in the 2009 MUTCD includes the requirement that a flagger (defined in Section 1A.13 as "a person") be stationed on each approach to the activity area to control vehicular traffic until the pilot vehicle is available.

Official Interpretation 6(09)-5 was issued in response to a request to replace the flaggers at each end of the long one-lane, two-way section of roadway with temporary traffic signals. Our interpretation was that such a replacement would violate the requirement in Paragraph 4 of Section 6C.13 that a person be stationed at each end of the section. However, our letter mentions that using temporary traffic control signals in addition to flaggers on each end of the section would be acceptable.

Even though we were not specifically asked the question as to whether an AFAD could be used to replace the flaggers at each end of the one-lane, two-way section of roadway, it occurred to us that the AFAD is another form of automatic device that could be used to stop the first driver in a manner in which the human interaction with the first driver is not present. Even though this question was not asked, we wanted to also address this related question in the same interpretation letter. By doing so, we did not mean to imply that a temporary traffic control signal and an AFAD are functionally equivalent to each other, or that an AFAD is a form of a temporary traffic control signal.

Temporary traffic control signals and AFADs are different from each other and have different functions and characteristics. The primary difference between them is that a temporary traffic control signal is operated automatically in a pretimed or vehicle-actuated manner, whereas an AFAD is manually operated by a flagger. An AFAD is not a temporary traffic control signal and should not be operated in an automatic manner.

For recordkeeping purposes, we have assigned the following official interpretation number and title: "6(09)-15 (I) — Clarification of Interpretation 6(09)-5." Please refer to this number in any future correspondence regarding this topic.

Thank you for your interest in improving the clarity of the provisions contained in Part 6 of the MUTCD. Please contact Mr. Ken Wood at or 708-283-4340 if you have any further questions concerning this matter.

Sincerely yours,

Original signed by:

Mark R. Kehrli
Director, Office of Transportation Operations