Maintain adequate funding and personnel levels to maximize efficient operation of traffic signal systems operations.

The City of Minneapolis Department of Public Works' experience.

February, 2004
Minneapolis,Minnesota,United States

Background (Show)

Lesson Learned

In February 2004, the National Transportation Operations Coalition (NTOC) Traffic Signal Action team utilized its recently developed self-assessment tool to provide the City of Minneapolis Department of Public Works with an assessment of its traffic signal management and operations program. The assessment team concluded that the city is working hard to keep the basic system elements running as efficiently as possible, but there are a number of issues or problems with the system that can be traced to inadequate levels of funding and personnel. A few examples include:
  • Failed detectors are not repaired;
  • Malfunctioning signals are left in flashing mode or four way stop control to minimize weekend overtime costs;
  • System performance measurements are not undertaken;
  • Operations are monitored by a traffic signal engineer only during the morning peak period
Based on their findings, the assessment team offered the following lessons learned:
  • Improve the funding for traffic signal operations. Considerable investment has been made in the cities' traffic signal systems, but without adequate funding to reverse system deterioration, the future costs to deal with the situation could rise dramatically. Due to budget shortfalls, little has been done to actively manage the system, nor has much been done to quantitatively assess current conditions. Consequently, it is not possible to determine how much more efficiently the system could be managed, and there is no way to quantify the level of investment necessary to reach various efficiency points.
  • Maintain adequate personnel levels. The assessment team concluded that inadequate personnel levels pose a significant problem to the future viability of the City system. Currently there are only two people responsible for operating the signal systems. Their workload includes day-to-day operations, signal retiming, management and quality control for contracting signal timing work, response to citizens' complaints, and response to legal inquiries on signal timing and operations. Given the size of the system, there should be at least five people in this group. Likewise, maintenance personnel are understaffed. The ITE Traffic Control System Operations manual estimates that an agency should have one traffic signal maintenance technician for every 31 traffic signals in the system, and The National Cooperative Highway Research Program Synthesis 245 suggests a range of 38-43 signals per technician. Based on these estimates, the maintenance personnel should be increased by at least three to five technicians in order to maintain the 800 signals within the city.

    There are key parts of the system that could greatly improve traffic conditions if adequate numbers of personnel were available. Specific examples are detailed below.
    • The SCOOT (Split Cycle Offset Optimization Technique) adaptive traffic signal system, installed in the central business district, has not been operational for three years, since some of the system detectors were removed during a construction project. Although these projects have restored the affected system hardware, no personnel time has been available to recalibrate the system. Hence the city is not able to reap the benefits (e.g., improved travel times) of its investment in the SCOOT system.
    • A central traffic signal management system has been installed at great expense, but currently an operator is scheduled to monitor the system only until 2 PM each weekday. This leaves the system relatively unattended during afternoon commute hours, as well as during planned events on weekends and holidays. Without an operator in attendance, the city cannot make the necessary adjustments to operations that might improve traffic conditions.
    • Routine functions, such as signal retiming, are not being performed on a regular basis. The limited staff is preoccupied with maintaining a basic level of operation.
A lack of resources and personnel has compromised the ability of the Department of Public Works to operate their systems. The city does not have the funding to adequately maintain its systems and to respond to problems in a timely manner. Through adequately funding operations and maintaining sufficient personnel, the city will be able to operate their systems more efficiently, thus maximizing safety and mobility benefits to drivers.

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Assessment of City of Minneapolis Traffic Signal Management and Operations Program

Author: National Transportation Operations Coalition Traffic Signal Action Team (NTOC), in association with AASHTO, ITE, ITS America, APWA, FHWA and University of Maryland

Published By: National Transportation Operations Coalition Traffic Signal Action Team (NTOC)

Source Date: February, 2004

URL: http://www.ci.minneapolis.mn.us/www/groups/public/@council/documents/webcontent/convert_274339.pdf

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Lesson Contact(s):

Paul Olson
FHWA Resource Center
720- 963-3239

Lesson Analyst:

Margaret Petrella
RITA/Volpe National Transportation Systems Center


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Lesson ID: 2007-00413