BACKGROUND
Traffic sensors are essential components of all highway traffic monitoring and traffic management systems and reporting. Traffic monitoring depends upon reliable detection and accurate measurement of flow rate, speed, classification, and other parameters for various modes of transportation. Active traffic management systems and other intelligent transportation systems applications require these parameters and more for varied uses like traffic control systems, wrong-way driving detection, near-miss crash analysis, and predictive analysis. Sensor systems based on new and emerging technologies—such as optics, electronics, communications, artificial intelligence, and connected and autonomous vehicle (CAV) applications—are rapidly supplanting traditional traffic sensor systems, but they typically lack independent evaluation of their accuracy and performance. State and local agencies must often rely on informal, inconclusive evaluations and pilot deployments to assess sensor systems’ suitability for highway applications. The burden to test every sensor type and revision that comes to market creates massive duplication of effort and wastes time, effort, and funding. Although millions of traffic sensors are in use, manufacturers and distributers can rarely provide independent third-party test results demonstrating their real-world performance. Sensor errors can seriously affect safety, mobility, and public trust. The lack of information regarding system performance and reliability in different operational domains can lead to misapplication of sensor systems, unacceptable performance, or short service life.
An authoritative method and a national testing program are needed to characterize the performance and identify the operational domains of current and emerging traffic sensor systems.
OBJECTIVE
The objective of this research is to develop evaluation criteria and testing methods for traffic monitoring sensors and systems, which could serve as the foundation for a national sensor system evaluation program.
Accomplishment of the project objective will require the following tasks, at a minimum.
TASKS
PHASE I – Planning
Task 1a. Conduct a state of the practice review of transportation sensor system evaluation criteria, methods, and programs. The review shall include current practice at state, local agencies, and manufacturers/suppliers.
Task 1b. Conduct a literature review of transportation sensor system evaluation criteria, methods, and programs. The review shall include guidelines and standards from American Society for Testing and Materials (ASTM), Institute of Electrical and Electronics Engineers (IEEE), the National Association of City Transportation Officials (NACTO), the American Association of State Highway and Transportation Officials' (AASHTO) National Transportation Product Evaluation Program, the Institute of Transportation Engineers (ITE), and National Electrical Manufactures Association (NEMA); and published and unpublished research conducted through the NCHRP, the Federal Highway Administration (FHWA), and other national, international, state, and pooled-fund sponsored research.
Task 2. Produce a report that contains the results of the state of the practice and literature reviews for Tasks 1a and 1b.
Task 3a. Propose criteria to be evaluated and the context in which they should be tested. Sensor measurements can include basic counts (number of vehicles, pedestrians or bikes), flow rate, speeds, occupancy, classification, etc. Target detection objects shall be inclusive and address potential biases such as size, color, shape, etc.
Examples of evaluation criteria shall include:
- Ground truth baseline
- Accuracy, reliability, and latency
- Service life
- Preventative maintenance requirements – hardware and software
- Ease of installation and calibration
- Security
- Backward compatibility
Examples of contexts shall include:
- Operational environment (weather, temperature, visibility, pavement type, etc.)
- Modal intention (vehicles, bicycles, micromobility, pedestrians, etc.)
- Traffic characteristics (flow rate, speeds, vehicle composition, etc.)
- Transportation facility characteristics (number of lanes, curvature, obstructions, etc.)
Task 3b. Outline repeatable testing methods for the traffic sensor system evaluation program that can be replicated by a geographically diverse network of laboratories.
Task 3c. Outline a feasible approach for the establishment of a national traffic sensor system evaluation program. The program structure should allow for adapting to a changing landscape of sensor hardware, firmware, and software versions. Program establishment costs, testing fee structure, and ongoing operational costs, including viable funding sources, should be considered. An example of a national testing protocol is the AASHTO’s National Transportation Product Evaluation Program.
Task 4. Prepare Interim Report No. 1 documenting the results of Tasks 1 through 3 and provide an updated plan for the remainder of the research no later than 6 months after contract award. The updated plan must describe the process and rationale for the work proposed for Phases II and III.
PHASE II – Program Development
Task 5a. Based on approved Interim Report No. 1, finalize evaluation criteria and testing contexts from Task 3a, combining them into an evaluation matrix.
Task 5b. Based on approved Interim Report No. 1, finalize and verify testing methods from Task 3b for the traffic sensor system evaluation program.
Task 5c. Based on approved Interim Report No. 1, finalize an approach for the establishment of a national traffic sensor system evaluation program.
Task 6. Propose and finalize a detailed outline for the guide for a National Traffic Sensor System Evaluation Program. The outline shall be approved by NCHRP before executing Task 7.
Task 7. Prepare the draft guide for a National Traffic Sensor System Evaluation Program based on Tasks 5a, 5b, 5c, and 6.
Task 8. Prepare Interim Report No. 2 that documents Tasks 5 through 7 and provide an updated work plan for the remainder of the research no later than 18 months after approval of Phase I. The updated plan must describe the process and rationale for the work proposed for Phase III.
Meet with the NCHRP to review the report and obtain approval for subsequent tasks.
PHASE III – Final Deliverables
Task 9. Address and update the guide based on comments from NCHRP project panel.
Task 10. Present the draft guide to appropriate AASHTO technical committees for comments and propose any revisions to NCHRP. Revise the guide after consideration of review comments. Task 9 must be completed before completing this task.
Task 11. Prepare the final deliverables including the final guide and the following:
- A conduct of research that documents the entire research effort and any lessons learned;
- Media and communication material (presentations, graphics, graphics interchange format (GIFs), press releases); and
- A stand-alone technical memorandum titled “Implementation of Research Findings and Products.”
STATUS: A research contractor has been selected for the project. The contracting process is underway.
