AGENDA #5c

 

 

MEMORANDUM

 

TO:                  Mayor and Town Council

 

FROM:            W. Calvin Horton, Town Manager

                       

SUBJECT:       Report on Engineering and Technological Alternatives for Improving Intersection

Safety and Operations

 

DATE:             September 9, 2002

 

 

The following information responds to the Council’s request for technological and/or engineering alternatives for improving safety at signalized intersections.

 

BACKGROUND

 

At its June 24, 2002 meeting, the Council received a petition from Ms. Michelle Barbee requesting that it reconsider its vote approving the installation of cameras to monitor red light violations at intersections.  The Council decided to proceed with the camera installation contract, and requested that a study of other engineering alternatives be done that could improve safety at signalized intersections.

 

DISCUSSION

 

Town staff regularly review literature and attend traffic engineering seminars that often include discussion of means and methods for improving intersection operations and safety.  In addition, the Town and NCDOT staff periodically review all signalized intersections for safe and effective operations.  The process includes field observations and review of geometric conditions, signal timing plans, and accident data.  If operational and/or safety deficiencies are identified, appropriate remedies are implemented and monitored for effectiveness.  These remedies may involve one or more of the following:

 

1.                  Geometric Improvements

2.                  Signal Timing Improvements

3.                  Technology Improvements

4.                  Enforcement Alternatives

 

1. Geometric improvements include:

 

·        Adding an additional through lane or turn lane to reduce delay and increase intersection capacity.

·        Identifying and removing sight obstructions that restrict the visibility of signal heads.

·        Reviewing, modifying, and/or supplementing signs and pavement markings to fully alert drivers to the posted speed limit and the presence of a signalized intersection.

 

 

2. Signal timing improvements include:

 

·        Checking clearance timings (yellow and all-red times) to ensure that they are appropriate based on criteria established in the Manual on Uniform Traffic Control Devices (MUTCD) and in accordance with requirements of the  NCDOT.

·        Checking signal timing cycle lengths (red, green, yellow and turn-arrow phases) for optimal operation of all critical lanes.

·        Checking signal timing plans to facilitate progression characteristics through each intersection and from intersection to intersection on travel corridors.

·        Checking vehicle detectors for proper location and operation to ensure that vehicles within or approaching intersections are detected and that applicable information is transmitted to the traffic signal controller.

·        Flashing signals during certain times of day or night to reduce unnecessary delay during off-peak periods.

 

3. Technology improvements include:

 

·        Installing highly visible large-diameter prismatic or polarized signal lenses at selected locations.

·        Replacing standard signal bulbs with high intensity light emitting diodes (LEDs).

·        Installing count-down pedestrian signals to improve message visibility and clarity, and audible pedestrian signals to aid visually impaired pedestrians.

 

We recently requested that the NCDOT allow us to experiment with “green flash” technology.  This technology would flash the green signal for the last few seconds of its cycle, thus alerting drivers of the impending change to yellow and providing a better opportunity for drivers to decide whether to stop or continue, depending on their proximity to the intersection and traffic conditions.

 

We have previously discussed the concept of extended yellow and/or extended all-red phases with the NCDOT.  We were advised that all signalized intersections must have engineered phasing plans based on accepted traffic engineering principles.   Extended yellow and/or extended all-red phasing is not standard practice and is not permitted on State roads in North Carolina for liability reasons.  We concur with the State on this issue.

 

4.  Enforcement alternatives include:

 

·        Police enforcement at selected locations.  The Police Department enforces traffic regulations at intersections to the extent possible with available resources and based on accident data, complaints and field observations.

·        Automated speed enforcement using a combination of electronic speed sensors and cameras.  This alternative would require enabling legislation from the General Assembly, which the Town has not requested to date.

·        Automatic red light enforcement using a combination of vehicle position sensors and cameras. At its May 29^th meeting, the Town Council authorized the Manager to negotiate a contract with ACS, Inc. to install cameras at several intersections in Town to monitor red light violations.  We are currently working on the draft contract document and expect to complete negotiations with the contractor within the next sixty days, after which program implementation will begin.

 

CONCLUSION

 

We continue to utilize engineering and technological alternatives whenever and wherever appropriate to optimize the safety and function of all signalized intersections system-wide. We will continue to monitor applicable literature and practices for new ideas and methods of improving intersection operations and safety.  Our objective is to provide clear and understandable intersection characteristics and regulatory equipment that provide the best opportunity for safe and efficient use by motorized vehicles, bicycles, and pedestrians.