Design, Safety, and Operational Considerations of Pedestrian Treatments at Intersections
Research Problem Statement
A number of pedestrian treatments have been developed for inclusion in intersection design over the years but research data that provides conclusive information about their effectiveness is lacking. Treatments include intersection geometry (including curb extensions/road narrowing and reduced curb return radius), in-pavement flashers, advance signing, messaging and beacons, signal features, medians and refuge islands, various methods of crosswalk markings (conventional striping, pavement texture changes, raised crosswalks), use of barriers such as fences or shrubs to discourage pedestrians from crossing at unsafe locations, and elimination of roadside obstacles that obscure visibility between pedestrians and vehicles. Roadway designers continually make judgments about the safety and viability of pedestrian features at intersections. Transportation agencies, as well as roadway engineers and urban designers, are looking for guidance about the effectiveness of various pedestrian accommodation treatments.
Incorporating features that are perceived to enhance pedestrian comfort and safety can have impacts on the design of the roadway for vehicle operations. An example is reducing the curb return radius to shorten pedestrian travel at a crossing can have the undesirable effect of impeding right turns by larger vehicles. Inclusion of median refuge areas at intersections can affect left turn operations, and can result in the misalignment of opposing left turning vehicles, compromising sight distance and the view of oncoming traffic.
Literature Search Summary
Right-turn interactions and channelized right turns/free-right turn lane design and impacts are the focus of NCHRP 3-72 and NCHRP 3-78, both currently underway. A few studies have been conducted on the effectiveness of in-pavement flashers and advanced warning messages such as “animated eyes”. There is substantial research that addresses good design practice to accommodate a specific mode but there is nothing found that evaluates the effect of pedestrian treatments on other intersection users.
Better information about the effects of pedestrian geometric intersection treatments in enhancing safety, complementing or impeding vehicle operations, and liability impacts to agencies incorporating these treatments is needed. Legal guidance is not proposed, but the research should identify what potential liability issues might exist. Objectives of the research would include guidance on design of treatments, guidance on the appropriate locations for treatments, and guidance on the trade offs between conflicting pedestrian and vehicle elements. The research should identify and develop a matrix to provide quick reference for responsible implementers on the appropriate use of pedestrian treatments at a variety of locations. Research should also consider the potential conflicts between pedestrian and bicycle treatments that occasionally arise in providing facilities for these modes.
The following tasks will need to be carried out to accomplish this project objective:
Task 1. Review the existing geometric design, and other relevant literature (both domestic and international) to (a) document the current state of practice with respect to pedestrian geometric intersection treatments, (b) document the safety records of the various treatments, (c) assess the effectiveness of the various treatments in a qualitative manner, both in terms of vehicle operations and pedestrian comfort and safety, (d) assess the effects of crossing distance and curb radius on intersection capacity, vehicle delay and pedestrian and vehicle safety(e) suggest changes to treatments as a result of the research effort.
Task 2. Select an appropriate number of sites with and without pedestrian safety treatments and conduct field studies that will allow the sites to be compared. Sites should be those utilized by as many different modes as possible and the interactions between the modes should be documented.
Task 3. Analyze vehicle operations for the above sites and document qualitatively at each location.
Task 4. Using the information generated in (2) above, model impact on vehicle operations and pedestrian safety with the goal in mind of recommending changes to designs for the treatments and guidance in the appropriateness of their use in a variety of environments.
Task 5. Submit a final report that documents the entire research effort, recommends design criteria and appropriate application for the pedestrian treatments. The report should comment on the effects of its recommendations on the classes of pedestrians including children, the elderly, and people with disabilities. Where appropriate, the report should include appendices with recommended language for the AASHTO Policy on Geometric Design of Highways and Streets; the AASHTO Guide for the Planning, Design, and Operation of Pedestrian Facilities; and other documents as appropriate.
Estimate of Problem Funding and Research Period
Urgency, Payoff Potential, and Implementation
State and local transportation agencies, and the design communities that apply their guidance documentation, would use the information obtained from the research project to develop guidelines for the intersection design for various facilities. This would result in a transportation system that better considers all modes and provides the safest design for all users, based on site-specific conditions. Documents that would potentially be affected are the AASHTO Policy on Geometric Design of Highways and Streets; and the AASHTO Guide for the Planning, Design, and Operation of Pedestrian Facilities.