Interpretation Letter 4-358(I) - Lateral Spacing of Supplemental Signal Faces

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U.S. Department of Transportation
Federal Highway Administration

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

March 5, 2009

In Reply Refer To: HOTO-1

Robert E. Vilak, Jr., P.E.
Traffic Engineer
Marion County Transportation Department
412 S.E. 25^th Avenue
Ocala, FL 34471

Dear Mr. Vilak:

Thank you for your February 24 letter requesting an official interpretation of item F of the second Standard statement in Section 4D.15 of the Manual on Uniform Traffic Control Devices (MUTCD), which states:

F. Required signal faces for through traffic on any one approach shall be located not less than 2.4 m (8 ft) apart measured horizontally perpendicular to the approach between the centers of the signal faces.

The key phrase in that sentence is "required signal faces." While some supplemental signal faces are totally optional, item D.1.b. of the same Standard statement requires a near-side supplemental signal face when both of the two primary signal faces for the major movement are more than 180 feet beyond the stop line. You are asking whether the minimum lateral separation of 8 feet between the "required signal faces for through traffic" must be simultaneously applied to the far-side primary faces and the "required" near-side supplemental face.

The intention of item F is to assure adequate lateral separation between immediately adjacent signal faces for the movement. It is not the intention of item F to require that a single near-side supplemental face be located directly in line longitudinally with one of the primary far-side faces. A supplemental near-side face, whether provided because of the longitudinal distance issue of item D.1.b. or for any other reason, may be located in any lateral position as long as the Guidance statement later in Section 4D.15 is followed:

If supplemental signal faces are used, they should be located to provide optimum visibility for the movement to be controlled.

However, if two or more supplemental near-side signal faces are provided for the through movement, then those multiple near-side faces shall be spaced laterally a minimum of 8 feet apart from each other.

I hope that this interpretation answers your question. Thank you for writing on this subject. If you have any questions, please contact Mr. Scott Wainwright of our staff by e-mail at scott.wainwright@dot.gov or by telephone at 202 366 0857. Please note that we have assigned your request the following official interpretation number and title: "4-358(I) - Lateral Spacing of Supplemental Signal Faces." Please refer to this number in any future correspondence regarding this issue.

Sincerely yours,

Original signed by:

Paul Pisano
Acting Director, Office of Transportation Operations

Incoming Letter

Marion County Transportation Department
412 S.E. 25^th Avenue
Ocala, Florida 34471
(352) 671-8686
Fax (352) 671-8687
One Team…One Mission

February 24, 2009

Office of Transportation Operations (HOTO)
Federal Highway Administration, Mail Stop: E84-402
1200 New Jersey Avenue, S.E.
Washington, DC 20590

RE: Request for Interpretation - MUTCD Section 4D.15

Mr. Wainwright:

I am writing to request a clarification of this section related to the use and location of "supplemental" signal heads. The MUTCD states the following:

D. Except where the width of an intersecting roadway or other conditions make it physically impractical:

A signal face installed to satisfy the requirements for left-turn signal faces (see Section 4D.06) and right-turn signal faces (see Section 4D.07), and at least one and preferably both of the two signal faces required for the major movement on the approach shall be located:
1. Not less than 12 m (40 ft) beyond the stop line.
2. Not more than 55 m (180 ft) beyond the stop line unless a supplemental near side signal face is provided.
3. As near as practical to the line of the driver's normal view, if mounted over the roadway.
Where the nearest signal face is located between 45 and 55 m (150 and 180 ft) beyond the stop line, engineering judgment of the conditions, including the worst-case visibility conditions, shall be used to determine if the provision of a supplemental near side signal face would be beneficial.

F. Required signal faces for through traffic on any one approach shall be located not less than 2.4 m (8 ft) apart measured horizontally perpendicular to the approach between the centers of the signal faces.

We have come upon several situations where the 180 ft maximum spacing beyond the stop bar is exceeded and the design and installation provide a supplemental signal head over the stop bar that is directly in line with the far side signal head.

Can the required 8 ft spacing between the centers of signal faces be overlooked in this application or should the supplemental near signal heads be mounted either to the left or right of the far side signals?

Thank you for your assistance regarding this matter,

Sincerely,

Robert E. Vilak, Jr, P.E.
Traffic Engineer
ph: (352) 671-8686
fax: (352) 671-8687
email: robert.vilak@marioncountyfl.org