Since the introduction of light-emitting diodes (LEDs) in traffic control systems, LEDs have been gaining in prominence to enhance attention and conspicuity of signs, create dynamic sign legends, and provide basic traffic control. The Manual on Uniform Traffic Control Devices (MUTCD) administered by the Federal Highway Administration (FHWA) has limited LED provisions to guide the LED applications, creating some indecision among public agencies relative to the appropriate application of LEDs in their traffic control applications.
The National Committee on Uniform Traffic Control Devices (NCUTCD) has submitted LED recommendations to FHWA that maintain basic traffic control concepts, recognize the adaptability of LED technology, and provide guidance for LED use. The development of those MUTCD recommendations identified a number of issues where research was not available to support the recommendations. There continues to be growing use of LED signs without clear understanding of possible safety advantages or impacts to machine vision, road users, and adjacent residents. To guide transportation agencies on basic traffic control concepts that warrant the life cycle of significant asset investments and safety to road users, research is needed to provide clarification on the LED applications in traffic control devices.
The objective of this research is to evaluate various LED sign applications and provide a guide to the effective use of LED applications in traffic control devices for the road user and current generation automotive machine vision systems.
Accomplishment of the project objective will require at least the following tasks.
PHASE I — Planning and Data Collection
Task 1. Conduct a literature review of relevant research and current state of the practice related to LED applications on traffic control devices. The review shall include published and unpublished research conducted through the NCHRP; FHWA; and other national, international, state, and pooled-fund sponsored research as it relates to human factors. The review shall also include identification and description of current generation automotive machine vision systems.
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 departments of transportation (DOTs), practitioners, automotive manufacturers, and relevant stakeholders. At a minimum, the proposed approach shall:
- Collect and summarize information to characterize the current state of the practice as well as future needs as it relates to LED applications in traffic control devices; and
- Identify the characteristics of current machine vision systems being deployed within North America.
Task 3. Execute the approved Task 2 methodology. Synthesize the results from Task 2 to identify knowledge gaps for (1) evaluating various LED applications and (2) managing LED applications in traffic control devices. These knowledge gaps should be addressed in this research or in the recommended future research as budget permits.
Task 4. Identify existing sections of MUTCD and National Electrical Manufacturers Association (NEMA) TS-4 standards that could be impacted by the results of the research findings.
Task 5. Propose a research plan to achieve the research objective to be fully developed in Phase II. At a minimum, the research plan shall address the following main topics and subtasks.
- Refresh Rate
- Identify appropriate refresh rates for LED signs in traffic control applications for machine vision consumption factors (e.g., ambient lighting, maintenance costs, contrast ratio, color, weather conditions, and sign sheetings), including traffic signals, beacons, hybrid signs, embedded within static sign LEDs, and LED signs.
- LED pitch (spacing)
- Identify potential uses of LED pitch or spacing to (1) display sign legend; and (2) provide sign recognition and legibility performance that at a minimum meets MUTCD and standard highway signs and markings (SHSM) legends, text, and symbols; and
- Assess standard changeable message signs (CMS) message elements and their ability to match the standard highway fonts, symbols, and other elements created to improve uniformity.
- Sign Shape
- Identify spacing characteristics of LEDs within or near the border needed to identify the standard shapes for the various signs and provide enhanced conspicuity; and
- Determine how to maintain standard sign shape consistency for day and night recognition.
Task 6. Develop resources from the findings of Task 3 to highlight potential implementation requirements, procedures (including quality assurance (QA)), strategies, and challenges as it relates to LED applications in traffic control devices.
Task 7. Prepare Interim Report No. 1 that documents the work completed in Tasks 1 through 6, and provides an updated and refined work plan for the remainder of the research no later than 6 months after the contract award date. The updated plan must describe the process and rationale for the work proposed for Phases II and III.
PHASE II — Research Plan Development
Task 8. Execute the approved Task 5 research plan according to the approved Interim Report No. 1.
Task 9. Develop proposed draft language for consideration by the NCUTCD to incorporate the research findings in the next update of the MUTCD (herein called the MUTCD Deliverable). The MUTCD Deliverable should identify potential solutions, which may include physical, electronic, or operational changes to traffic control devices for machine vision that meet the needs of human drivers and automated driving systems.
Task 10. Prepare Interim Report No. 2 that documents the results of Tasks 8 and 9 and provides an updated work plan for the remainder of the project. This report should include revised examples of materials and resources developed in Task 6 to be incorporated into the contractor’s final research report. The updated plan must describe the work proposed for Phase III.
PHASE III — Final Products
Task 11. Revise the MUTCD Deliverable considering the NCHRP’s review comments. Present the MUTCD Deliverable to all relevant NCUTCD Technical Committees and Joint Task Forces and propose any revisions to NCHRP.
Task 12. Prepare a final deliverable that documents the entire research effort. Final deliverables should include (1) a final research report documenting the entire research effort and findings; (2) the MUTCD Deliverable; (3) prioritized recommendations for future research; (4) presentation material and resources; and (5) technical memorandum on implementation.
STATUS: Proposals have been received in response to the RFP. The project panel will meet to select a contractor to perform the work.