This report provides a guideline to estimate the staffing and resource needs required to effectively operate and maintain traffic signal systems. In 2007, the NTOC Traffic Signal Report Card (TSRC) assigned a grade of D nationally to how agency programs support the efficient operation and maintenance of traffic signals (5). The D grade indicates that relative to what is considered "good practice", overwhelmingly an ad-hoc approach is taken, resulting in some positive outcomes, but generally agency programs are not as effective as they could be.
In surveys of practitioners and national experts completed by the FHWA, it was recognized that no clear definition of traffic signal operations has been developed and no consensus appears to exist as to what activities are required to support traffic signal operations. The lack of a concise definition of traffic signal operations provides some insight into why practices, staffing levels, objectives and performance measures are divergent in this area. Operating agencies clearly understand the requirements for adequate traffic signal maintenance. The results of several surveys indicate that many agencies tend to be primarily focused on maintenance activities, with most of their attention focused on keeping traffic signals operating (turning green, yellow and red) and little attention on making the operation efficient on a 24/7 basis. This has some safety implications and contributes to millions of hours of unnecessary traffic delays and congestion.
A working definition of traffic signal operations is the active prioritization of objectives and collection of information to efficiently manage traffic signal infrastructure and control devices to maximize safety and throughput while minimizing delays. The working definition of traffic signal maintenance is the preventative and responsive activities to preserve traffic signal infrastructure and control devices necessary for the safe and efficient utilization of arterial, collector and local roadways. The discussion of resource requirements in this report will refer to the definitions of traffic signal operations and maintenance as stated above.
Initially, it was envisioned that this report would verify and update the resource requirements (staffing levels and criteria or levels of staff experience and training) provided in a number of publications including the ITE Traffic Engineering Handbook and FHWA Traffic Control Handbook. The results of a survey performed under this project, as well as a review of the literature and other surveys indicated that agencies achieving a high level of signal system performance do so under a wide variety of conditions such as agency size, geography, system complexity and traffic conditions that do not adhere to the typical level of documented resource requirements. Accordingly, a set of performance-based criteria were developed to define requirements. The performance-based criteria are focused on establishing realistic and concise operations objectives and performance measures. The operations objectives and performance measures dictate the staffing and resource level required for their achievement.
Research indicated that while maintenance was, in general, timely, and that agencies used effective tools such as Synchro to develop signal timing plans, significant deficiencies resulted from a failure to systematically determine the need for signal retiming and to retime at appropriate intervals. This result is closely related to not clearly establishing and documenting specific operations objectives and programs to measure performance.
Key management and operations criteria and recommendations to attain effective traffic signal operations and maintenance include:
- Management controls. Staff qualifications and periodic updating of management plans. Management plans should include a mission statement, strategic plan, objectives and measures, periodic collection and review of performance data and remedy of deficiencies in signal timing and other system characteristics. Recommendations concerning communication paths with the public and other stakeholders are also described.
- Signal timing design. Signal timing performance should be reviewed at periods established by management plans but should not exceed 30 to 36 month periods. Signals should be retimed using an accepted methodology. A methodology for determining the number of daily timing plans required as well as weekend and special function timing plans should be utilized.
- Operations. Functional changes in requirements such as pedestrian needs, transit and preemption requirements, etc. should be periodically reviewed and addressed. Criteria are provided for the persistent monitoring of traffic systems.
- Maintenance. Since maintenance response time for failure repair after the agency has been notified of failure is generally good and the ability to automatically detect failures at isolated intersections is poor, a criterion to improve this capability was established. Recommendations for the up-time for detectors are provided.
The report provides recommended personnel staffing, training and experience levels.previous | next