Challenge
State departments of transportation (DOTs) are increasingly using automated systems to monitor and manage traffic signals. Over the past decade, interest in automated traffic signal performance measures (ATSPMs) has grown quickly, yet adoption across agencies has been uneven. Some state DOTs are leading deployment, while others face barriers related to funding, equipment upgrades, staffing, and organizational capacity.
ATSPMs use high-resolution signal and detector data to support the continuous and proactive monitoring of traffic operations and maintenance. Signal state and detector events can be collected up to 10 times per second, creating a level of detail that allows agencies to better understand traffic flow, signal performance, and system maintenance needs. Even with these capabilities, agencies vary widely in how they plan, manage, operate, and maintain these systems.
Understanding why some agencies sustain and expand their programs while others do not is an important step toward improving the use of ATSPMs nationwide. The Synthesis research conducted by the National Cooperative Highway Research Program (NCHRP) was initiated to document the current state of practice and to identify lessons that could help agencies make informed decisions about implementation and long-term use of ATSPMs.
Solution
Our team led the full synthesis effort and worked to understand how state DOTs are addressing automated traffic signal performance, including both the traditional approaches, like using signal controller and detector data, and emerging approaches, like incorporating crowdsourced and connected data sources.
To develop a broad view of current practice, the team gathered input from 42 state DOTs through an online survey. This provided a strong national sample of agency experiences and approaches. The research also included five in-depth case examples that explored agencies with varying levels of deployment.
The work examined how agencies manage automated traffic signal performance systems, how they integrate them into daily operations and maintenance, and how they address common challenges. It also documented funding strategies, staffing considerations, organizational factors, and lessons learned from implementation.
Findings were synthesized and presented in NCHRP Synthesis 659: Automated Traffic Signal Performance Measures: Management, Operation, and Maintenance. The report describes the current state of practice and highlights key findings from the national survey and case examples. Case examples include DOTs in North Carolina, Maryland, Minnesota, Georgia, and Utah.
The Outcome
How State DOTs Are Using Data to Rethink Traffic Signal Performance
The synthesis provides a national snapshot of how state DOTs are planning, managing, operating, and maintaining automated traffic signal performance systems. By documenting both successes and challenges, the study offers practical insights into the factors that support sustained deployment and expansion of these systems. Additionally, the synthesis suggests future research efforts to address the knowledge gaps identified in this study.
The report also gives agencies a clearer understanding of how automated systems can enhance traffic operations across corridors and networks, as well as of how detailed data can support continuous monitoring and maintenance.
By bringing together survey results, case examples, and lessons learned, the study both helps transportation professionals better understand current practices and supports informed decision-making about the future use of ATSPMs.
