OBJECTIVE
The objective of this research was to develop a comprehensive guide to enhance the safe operation for all users of unsignalized intersections. The guide should be practical and multimodal and aid practitioners in selecting design, operational, maintenance, enforcement, and other types of treatments to improve safety, mobility, and accessibility.
BACKGROUND
Approximately 90% of intersections in the United States are unsignalized with over 6,000 fatalities estimated to have occurred at these types of intersections in 2007 (
Safety at Unsignalized Intersections Presentation, FHWA). It is vital that state and local transportation agencies consider how the design and operation of unsignalized intersections can better address safety performance, operations, multimodal needs, and other impacts. A majority of unsignalized intersections are owned and operated by local agencies. Many smaller jurisdictions do not have professional engineers on staff but must frequently make decisions on treatments at unsignalized intersections. All transportation agencies need practical guidance to assist them in arriving at and justifying these decisions to policy makers and the public.
TASKS
Task 1. Review pertinent domestic and international literature on the analysis and improvement of unsignalized intersection safety and operation to identify material that can be incorporated into the guide. Tabulate key documents that will be referenced in the guide by topic.
Task 2. Identify audience segments for the guide. Develop and execute an outreach plan for determining how members of these audience segments would use the guide.
Task 3. Develop a practical typology for diagnosing safety, mobility, and accessibility issues at unsignalized intersections. The typology should be sensitive to the context of the intersection (e.g., proximity to a transit stop, type and density of development, terrain) and useful for selecting treatments at existing intersections and new designs. The typology should also reflect the characteristics of the intersection (e.g., traffic volumes, geometrics).
Task 4. Identify treatments that can be applied to unsignalized intersections to address safety, mobility, and accessibility concerns. This inventory of treatments should include maintenance, enforcement, and other types of treatments in addition to traditional engineering ones. The descriptions of the treatments should include typical applications and include any educational or other activities needed to implement the treatment.
Task 5.. Describe the criteria and data that a state or local transportation agency should consider in developing a plan for prioritizing unsignalized intersections for improvement. A preferred prioritization process is not expected since each agency has its unique constraints and existing processes.
Task 6. Develop an organizational structure for the guide, illustrating how the following points will be handled:
- Ease of navigation for the user to find the needed information,
- Incorporation of nonmotorized users throughout the guide,
- Generous use of graphics and figures,
- Emphasis on practical guidance rather than theory, and
- Appropriate use of references for detailed information.
Task 7. Prepare an interim report summarizing the results of Tasks 1 through 6. Meet with the NCHRP project oversight panel for the review and approval of the interim report.
Task 8. Prepare the guide based on the approved organizational structure. The guide should be well organized and easy to read. Graphics, pictures, and charts should be extensively used to make the guide more readable. In general, the guide should refer to other documents for specific information on treatments. The guide should address all modes (including cars, trucks, transit, bicycles, and pedestrians) and help practitioners to:
- Quickly diagnose safety, mobility, and accessibility issues at an intersection,
- Identify and recommend a range of effective treatments to address the diagnosed issues,
- Estimate or describe the positive and negative impacts of the treatments at the intersection and on the corridor, and
- Explain their decisions (including a decision to not modify the intersection) to the public and policy makers.
The guide should discuss how the information could be applied in a systemic, proactive manner, including practical approaches to prioritizing intersections for improvement.
Task 9. Develop a final report that documents the entire research effort and includes the Task 8 guide as a stand-alone appendix.
