Traffic Signal Location

Question

Traffic Signal Location

TLCPA (Electrical)

(OP)

17 Jul 10 09:05

I am an EE that noticed what I think is a problem with traffic signals located on the far side of the intersection. Drivers are looking at the signal and will stop for a red light where they can see the signal. Stop Here On Red signs and painted stop lines are not seen (they are looking at the signal) or ignored. Consequently stopped vehicles are in the crosswalk or worse yet in the intersection. Another problem is following a truck through the intersection. You cannot see the signal over the truck until you are in the intersection. If the traffic signal was on the near side of the intersection drivers would still stop where they can see the signal without being in the crosswalk or the intersection and you will be able to see the signal before you enter the intersection when following a truck. I think this is a better way to keep vehicles out of the "box." What say you?

ACtrafficengr (Civil/Environmental) · Answer 1 · 2010-07-19 09:18:26

Technically, this is a Manual on Uniform Traffic Control Devices (MUTCD) topic, but since I don't think Eng-Tips has an MUTCD forum, I won't object.

You could try posting your question on FHWA's MUTCD forum: http://knowledge.fhwa.dot.gov/cops/opspublic.nsf/home?openform&Group=Signals&tab=DISCUSSION&COLLAPSE=

This is what the MUTCD says about longitudinal placement of signal heads:

Quote:

Section 4D.14 Longitudinal Positioning of Signal Faces
Standard:
01 Except where the width of an intersecting roadway or other conditions make it physically impractical, the signal faces for each approach to an intersection or a midblock location shall be provided as follows:
A. A signal face installed to satisfy the requirements for primary left-turn signal faces (see Sections 4D.17 through 4D.20) and primary right-turn signal faces (see Sections 4D.21 through 4D.24), and at least one and preferably both of the minimum of two primary signal faces required for the through movement (or the major turning movement if there is no through movement) on the approach shall be located:
1. No less than 40 feet beyond the stop line,
2. No more than 180 feet beyond the stop line unless a supplemental near-side signal face is provided, and
3. As near as practical to the line of the driver's normal view, if mounted over the roadway.
The primary signal face that satisfies this requirement shall simultaneously satisfy the lateral placement requirement described in Section 4D.13 (see Figure 4D-4).
B. Where the nearest signal face is located between 150 and 180 feet 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.
Support:
02 Section 4D.11 contains additional provisions regarding longitudinal positioning of signal faces for approaches having a posted or 85th-percentile speed of 45 mph or higher.
Guidance:
03 Supplemental near-side signal faces should be located as near as practical to the stop line.

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

Come Join Us!

Posting Guidelines

Traffic Signal Location