AGENDA #5d
MEMORANDUM
TO: Mayor and Town Council
FROM: W. Calvin Horton, Town Manager
SUBJECT: Report on Inquiries about Traffic Signal Operations and Modifications at Various
Locations in Chapel Hill
DATE: March 6, 2000
(This report responds to Council inquiries about the operation of certain traffic signals, alternative types of traffic signal equipment, and possible traffic signal modifications to improve pedestrian accommodations.
During a Council meeting in January of this year, a Council member inquired about traffic signal operations at the Morehead Planetarium pedestrian crossing on East Franklin Street and at the East Franklin Street crossing just west of Henderson Street in front of the post office. We were requested to ensure that the equipment serving the pedestrian crossings was functioning properly. We visited both locations and determined that all equipment is functioning as intended.
The traffic signals located along East Franklin Street are coordinated for efficient vehicle flow, while still maintaining service for intersecting side streets and pedestrian crossings. Most of the traffic signals located in the downtown area operate under pre-timed or semi-actuated conditions.
· A pre-timed traffic signal operates under a set amount of time (a cycle length) and will cycle through to service all approaches, regardless of whether or not vehicles/pedestrians are present.
· A semi-actuated traffic signal provides detection for minor approaches (side streets) only. It is used where a major street has relatively uniform traffic flow, and an intersecting minor street has low volumes with random peaks. By interrupting traffic flow on a major street, a semi-actuated traffic signal provides an opportunity for traffic on a minor street to access or cross a major street.
The traffic signal located at the Morehead Planetarium pedestrian crossing is a semi-actuated traffic signal with pedestrian pushbuttons. Traffic flow on East Franklin Street will be stopped when the pedestrian pushbuttons activate the traffic signal heads. However, this is not an instantaneous process. The traffic signal can only stop traffic flow on East Franklin Street at certain times in its cycle length. We have made adjustments in the traffic signal coordination timings to minimize to the extent possible the delay experienced by pedestrians waiting to cross East Franklin Street at this location.
The traffic signal located at the East Franklin Street pedestrian crossing in front of the post office operates under pre-timed conditions. There are no pedestrian pushbuttons at this location, which means that the pedestrian signal heads are activated, whether pedestrians are present or not, in accordance with pre-determined traffic signal timings. The signal coordination timings at this location have also been adjusted to provide for the best possible pedestrian crossing conditions.
Traffic signal heads mounted on corner posts.
During the November 8, 1999 Council meeting, a Council member requested information regarding the use of pole-mounted traffic signals located on the intersection corners instead of overhead traffic signals attached to span wires or mast arms.
In the past, traffic signals were typically mounted on poles located on the corners of intersections. Although no longer a common practice in this country, pole-mounted signals can still be found in historic districts and inner-city areas in many states.
The Manual on Uniform Traffic Control Devices (MUTCD) provides widely accepted standards for designing traffic signal installations. The MUTCD does not specifically preclude the use of pole-mounted traffic signals. However, the standards for necessary design criteria such as minimum visibility distance, signal head configuration, and number of signal faces are difficult to achieve under most circumstances using pole-mounted traffic signals.
North Carolina State law requires that traffic control devices on both State and municipal street systems must conform to the MUTCD. The NC Department of Transportation has developed its standards and guidelines based on the MUTCD. The majority of the traffic signals located in Chapel Hill are on state roads and must meet state standards. Those traffic signals located on town-owned streets must conform to the MUTCD.
After reviewing the signalized intersections in Chapel Hill, we did not identify any locations where we would recommend converting overhead traffic signal installations to pole-mounted installations for the purpose of improving service or safety for vehicles or pedestrians.
During its October 27, 1999 meeting, the Council requested that we investigate the possibility of an exclusive pedestrian phase at the intersection of East Franklin Street and Elliot Road. During such a phase, vehicles would be required to stop simultaneously at all legs of the intersection to allow pedestrians to cross in all directions.
We previously informed the Council that the State had approved traffic signal improvements at the East Franklin Street/Elliot Road intersection including the installation of pedestrian signal heads with pushbuttons for both crosswalks on East Franklin Street and the one on the east side of Elliot Road. (Please refer to the attached March 12, 1999 letter from Mr. Patrick Wilson with the NC DOT Division 7 Office.) These improvements have been funded and we anticipate the installation to be completed by the fall of this year. The installation of pedestrian signal heads with pushbuttons for the crosswalk on the west side of Elliot Road will be completed by the Franklin Grove Townhomes development, as one of the stipulations in the development’s special use permit.
We discussed with the State the possibility of modifying the traffic signal operations at this intersection to include an exclusive pedestrian phase. Based on an analysis of traffic data collected at the intersection (which included counting the number of pedestrians crossing at the crosswalks), the State does not believe that such a modification is necessary at this time. However, if conditions change significantly, the State has agreed to re-evaluate the intersection with consideration of an exclusive pedestrian traffic signal phase. We will continue to monitor this location for changes in pedestrian traffic.
1. March 12, 1999, Wilson letter. (p. 4)