BACKGROUND

In the United States, more than 300,000 traffic signals are currently in operation. To maintain the operation and performance of traffic signals, state departments of transportation (DOTs) have relied on manual counts entered into signal software (i.e., Synchro) and simulation models (i.e., Vissim) to develop traffic signal timings. These timing calculations are often retained unless an agency receives public complaints, although the performance may have degraded gradually over time as travel demand changes. Automated traffic signal performance measures (ATSPMs) could provide additional information to DOTs to help improve signal performance at intersections.

ATSPMs started in the mid-2000s with the collection and analysis of high-resolution event-based data for traffic signal performance. Since then, conducted research has advanced the development of a schema method using event-based data for assessing and improving the performance of traffic signals, traffic signal systems, and traffic signal system business practices. ATSPM systems primarily present raw data in graphic representation to provide visual tools to assist signal operators in assessing signal performance on a regular basis, proactively identifying problems associated with signal timing, and to seek opportunities for improving traffic signal operation to improve traffic flow and system efficiency.

However, ATSPMs user experiences have identified limitations of the current high-resolution data schema on which the ATSPMs are established including:

• The unavailability of a universal schema or easy conversion from one data format to another for different types of systems, causing state DOTs and public agencies to duplicate their effort in creating and managing data and information. In addition, due to limited standardized guidelines about managing high-resolution signal data and associated metadata information, state DOTs and other public agencies may handle complex traffic signal system cases slightly different, which can lead to inconsistent methodologies between agencies.
• Connected automated vehicles (CAV) and sensor technology, a new data source of short-term trajectory information as vehicles and pedestrians approach an intersection, are currently not included in the data schema for ATSPMs.
• The unavailability of a well-documented standard available for recording geo-spatial metadata.

Research is needed to define effective practices for state DOTs and public agencies for managing ATSPM data long-term and ensure these practices are scalable, transferable, and enable CAV integration.

OBJECTIVE

The objective of this research is to develop a guide to assist state DOTs and public agencies with long-term management of Automatic Traffic Signal Performance Measurement (ATSPM) systems applications for scalability, transferability, and CAV integration.

TASKS

PHASE I — Planning and Data Collection

Task 1. Conduct a literature review of relevant research and current state-of-practice related to ATSPM systems. The review task will also identify state agencies that have taken leading roles in the development and implementation of ATSPMs and other relevant technologies, particularly those facilitating the measurement of vehicle trajectories in the field.

Task 2. Propose a methodical approach (e.g., surveys, targeted interviews, focus groups, and other appropriate methods and/or tools) to collect information from state DOTs, practitioners, and relevant stakeholders involved in the management and operation of traffic signals. The proposed approach shall collect and summarize information to characterize the current state-of-practice as well as future needs including the following:

• Diverse approaches employed to resolve intersection metadata issues (e.g., conception of an intersection in Society of Automotive Engineers (SAE) J2945 standard as compared to methods of describing detector layouts for signal control, phase convention, detector number assignment, etc.);
• Data storage issues for data obtained from numerous sources (e.g., controller, vehicle-to-everything (V2X), third party point/probe (e.g., bluetooth technology), etc.) and data collection practices (e.g., data retention, data retrieval, data fidelity, etc.);
• Detection information, such as detector type, capabilities, data obtained, and relevant ATSPM use cases that employ this data;
• Multi-modal (including transit, pedestrians and non-motorized vehicles) traffic signal performance measures and extended use cases;
• Limitations of high-resolution data on which ATSPMs are established (e.g., high-resolution controller data only storing changes in states (i.e., event codes), recording frequency, etc.);
• Identification of data currently used for signal performance measures related to non-personal vehicles and the related data that is needed to provide an enhanced and more holistic view of intersection performance; and
• Inclusion of other industries involved in surrogate activities that might provide useful insights into the processing, archiving and management of data.

Task 3. Execute Task 2. Synthesize the results of Tasks 1 and 2 to identify knowledge gaps for implementing and managing the life-cycle of ATSPM systems. These knowledge gaps should be addressed in this research or in the recommended future research as budget permits.

Task 4. Propose a methodology to describe the approach to gathering necessary resources and prepare the guidelines to achieve the research objective.  This methodology will describe the procedures to achieve the research objective in Phase II. At a minimum, the methodology shall:

• Identify the potential data exchange standards and requirements (e.g., SAE J2945, etc.) to ensure compatibility and continuous flow of data from implementation to signal management;
• Evaluate existing techniques, schemas, and technologies for storing the data for an intersection to include short-term trajectory information derived from CAVs or other detection technologies;
• Develop data compression and aggregations methods to enable long-term storage of critical information to manage the reduction and processing speed of the system;
• Analyze the data’s life-cycle from data creation, data use to data archiving to provide guidelines for efficient management;
• Develop a criteria-based assessment to assist state DOTs and public agencies, to include, but not be limited to, hardware requirements, user capability functions, and data input/output format compatibility;
• Propose a schema for saving geospatial information required for current ATSPM systems; and
• Develop resources that identify potential implementation requirements, procedures (including quality control (QC) and quality assurance (QA)), strategies, training needs, and challenges as they relate to ATSPM systems.

Task 5. Develop a preliminary outline for the guide based on the proposed methodology.

Task 6. Prepare Interim Report No. 1 that documents the work completed in Tasks 1 through 5. The updated plan must describe the work proposed for Phase II through IV.

PHASE II — Methodology Development

Task 7.  Execute the methodology according to the approved Interim Report No.1. The execution of the methodology will generate the material for the guide in Phase III.

Task 8. Provide a detailed description of each chapter and section of the proposed guide and complete a sample chapter of the proposed guide selected by NCHRP. This chapter should be publication-ready.

Task 9. Prepare Interim Report No. 2 that documents the results of Tasks 7 and 8 and provides an updated work plan for the remainder of the project. The updated plan must describe the work proposed for Phases III and IV.

PHASE III — Guide Development

Task 10. Develop the guide according to the approved Interim Report No. 2.

Task 11. After NCHRP approval of the draft guide, plan and conduct workshop with 20 representatives of DOTs and other stakeholders to review the draft guide and implementation plan. Revise the draft guide according to the outcomes of the workshop. The invited representatives shall be approved by NCHRP.

Task 12. Prepare Interim Report No. 3 that documents the results of Tasks 10 and 11 no later than 8 months after approval of Phase III. The updated work plan must describe the work proposed for Phase IV.

PHASE IV — Final Products

Task 13. Revise the draft guide and workshop materials considering the NCHRP’s review comments.

Task 14. Submit the final deliverables including (1) a final research report documenting the entire research effort and findings; (2) the guide as a stand-alone document; (3) prioritized recommendations for future research; (4) presentation material (e.g., workshop materials); and (5) technical memorandum on implementation.