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Safety, Operations, and Usability Trade-offs between User Groups at Intersections

Research Problem Statement


Current geometric design guidelines for highways and streets do not adequately anticipate or accommodate the needs of all potential users. Pedestrians and bicycles are common users of the urban and rural transportation network, especially at intersections. Designs that accommodate their needs are often viewed as retrofit or add-ons rather then as being given equal importance. There are several issues related to safety of the users and the identification of the unique problems that these users experience is of utmost importance.  Therefore, having an understanding of the problems and issues for these users, solutions could be sought to reduce, if not eliminate, potential problems. A possible approach for addressing this issue is the trade off between design elements for vehicles and other users.  However, there is little knowledge as to the safety consequences from such design element trade offs. 


Literature Search Summary


There is limited research in this subject area.  Several studies have been conducted that dealt with the safety of the various non-vehicle roadway users but little has been done to correlate the design element trade offs that can be implemented to improve the safety and operational level for the non-vehicle roadway users. There has been limited work that could form the basis for this work and include:


·                    NCHRP Project 15-20, “Planning, Design, and Operation of Pedestrian Facilities.”  The objectives of this recently completed research were to develop a guide for planning and designing pedestrian facilities. The findings of the study are to be considered for incorporation in the next edition of the Green Book.


·                    AASHTO design guides (A Policy on Geometric Design for Highways and Streets; Guide for Developing Bicycle Facilities; and Guide for the Planning, Design and Operation of Pedestrian Facilities)


·                    ADA requirements and guidance


Research Objective


The objective of this research is to develop guidelines for addressing the needs of roadway users especially at intersections. The work to be completed should address the trade offs between design elements and safety and operational performance of these facilities.

The research should include a literature review of previous research and current practice in regard to pedestrian and bicycle facilities design, development of a work plan to achieve the research objectives, collection of applicable field data and other information, evaluation of the safety and operational effects of various combinations of design elements, and preparation of a final report.  The final report should include proposed changes to AASHTO Policy, if results support a change.


Estimate of Problem Funding and Research Period


Recommended Funding:  



Research Period: 

30 months


Urgency, Payoff Potential, and Implementation


This research topic was selected by the AASHTO Technical Committee on Geometric Design, the TRB Committee on Geometric Design, and the TRB Committee on Operational Effects of Geometrics at their combined meeting in June 2004 as one of the high priorities for research. The research is needed to fill performance gaps in current roadway design to address and accommodate the needs of all roadway users. It will be of use in the design of highways nationwide.

Sponsoring Committee:AKD10, Performance Effects on Geometric Design
Date Posted:06/01/2007
Date Modified:06/04/2007
Index Terms:User benefits, Highway safety, Usability, Highway operations, Intersections, Highway design, Crosswalks, Pedestrian movement, Pedestrian safety, Bicycle travel, Bicycles,
Cosponsoring Committees: 
Pedestrians and Bicyclists
Operations and Traffic Management
Safety and Human Factors

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