Signal Timing Strategies for Non-Motorized Users

Over the last decade, there has been increased interest in promoting active and sustainable transportation modes such as bicycling and walking, as a means to alleviate congestion, lower emission levels and improve personal health. Most of the walking and bicycling trips occur in urban areas, where signalized intersections are fairly common. The 2009 National Household Travel Survey (NHTS) estimated 42 billion walking trips per year, accounting for 10.9% of all trips undertaken. Additionally, bicycle trips increased from 0.7% of total trips in 1995 to 1.0% in 2009. Pedestrians often face unnecessary delays due to the traditional focus on prioritizing vehicular movements at signalized intersections. Additionally, most of the walking trips are short; a nationwide survey showed that 67% of walking trips are 1 mile or shorter in length. Because walking trips are shorter and signal timing is optimized for motor vehicles, delays at signalized intersections tend to affect pedestrians disproportionately compared to auto trips. Several studies have shown that delay is a key factor in pedestrian non-compliance. The Highway Capacity Manual (HCM) states that delays greater than 30 seconds are associated with increased frustration and risky behaviors. On the other hand, while bicycles are commonly served concurrently with vehicular movements, with the increasing number of cycle tracks co-located with roadways and the move towards protected intersection installations in specific locations, there is a need to focus on studying the efficiency of signal timing at locations with bicycle-specific infrastructure. There has only been a limited amount of research on this subject in the U.S. Although the number of bicyclists and pedestrians is increasing, safety remains a top concern and can be a limiting factor in encouraging walking and especially in engaging new cyclists. According to National Highway Traffic Safety Administration, there were 4,884 pedestrian and 726 bicyclist fatalities and an estimated 65,000 and 50,000 pedestrian and bicyclist injuries in 2014 respectively. For both modes, majority of the fatalities occurred in urban areas, with 19% of pedestrian fatalities and 31% of bicyclist fatalities occurring at intersections. Pedestrian safety research at intersections has focused on lack of driver yielding, pedestrian non-compliance, and pedestrian visibility and the emergence of countermeasures such as countdown pedestrian signals, leading pedestrian intervals and exclusive pedestrian phasing. Given that bicycle traffic in the U.S. is typically served in the same lane as motor vehicle traffic or an immediately adjacent bicycle lane, much recent research has been focused on improving the safety of bicycles in the traffic stream. However, most of this research has focused on design treatments, with little to no research available on signal timing treatments for improving bicycle safety. The goal of signal timing at an intersection should be to separate conflicting movements in time, maximizing safety and efficiency for all users. In many jurisdictions, however, signal timing objectives have traditionally focused on facilitating vehicle progression and reducing vehicular delay and stops. While these are important considerations in many contexts, other users, specifically bicycles and pedestrians, deserve similar focus and control strategies. Recent updates to the Highway Capacity Manual (HCM) have expanded modeling techniques for these users, but the overall approach remains largely vehicle-focused. Even when the analyst chooses to perform a multimodal analysis, very little guidance is provided for signal timing practices. Design guidance is available, but these focus on geometric treatments more than signal timing. The Signal Timing Manual outlines basic information on pedestrian and bicycle signal timing, but does not provide detailed information for selecting different timing strategies. In recent years, a few researchers have investigated specific topics within the larger scope of multimodal operation, but there has been no comprehensive development of a toolbox of timing strategies focused on improving the safety and efficiency of multimodal operations at signalized intersections. Similarly, there is considerable expectation of operational benefit from connected vehicles, but very little discussion of whether or how these technologies might impact non-motorized modes of traffic. This research will help address the lack of guidance for signal timing strategies to better accommodate multimodal users. The main research outcome will be a guide for practitioners which integrates both novel signal retiming strategies (that have been proven to work well) and the findings of previous studies. An emphasis will be given to a comprehensive investigation of the efficiency and safety impacts of various multimodal treatments at conventional signalized intersections, but opportunities will be addressed for similar future studies on the intersections with multimodal specific infrastructure and intersections with alternative geometries such as diverging diamond interchanges (DDIs), continuous flow intersections (CFIs), and others. Tasks anticipated in this project include the following: (1) Review literature to identify deficiencies in current practice as well as the findings of research works attempting to address those deficiencies. (2) Interface with City, County, and State transportation officials to identify traditional multimodal signal timing problems perceived by practitioners as well as those experienced when addressing these users at locations with multimodal specific infrastructure. (3) Propose, test, and analyze various multimodal timing strategies at signalized intersections. (4) Use video based conflict analysis and/or surrogate safety measures to identify safety impacts. (5) Characterize the system components (level of detection, type of controller or controller software, type of communication system, etc.) necessary for successful deployment of these timing strategies. Identify levels of maintenance, support, and expertise a managing agency would need to make effective use of these strategies. (6) Develop a tiered set of recommendations for agencies and agency personnel based upon the operational objectives of the agency and specific intersections to enable the effective use of the strategies developed within this work. Implement a set of recommendations developed in prior tasks in the field to allow for validation. (7) Develop a set of recommendations scoped for assisting agencies across a spectrum of budget constraints and personnel capabilities to implement and utilize these timing strategies. The work will help improve the safety and efficiency of vulnerable users at signalized intersections, something which historically not been the matter of focus. It will provide a suite of signal timing strategies and recommendations for agencies at various capability levels, and will cover a wide range of contexts ranging from isolated rural intersections to complex urban intersections that are members of an arterial or grid network. The research products will fill a void on guidance for multimodal signal timing that is urgently needed at a time when these travel modes are increasingly emphasized in street designs.

Language

  • English

Project

  • Status: Proposed
  • Funding: $500000
  • Contract Numbers:

    Project 03-133

  • Sponsor Organizations:

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Sundstrom, Lori

  • Start Date: 20170512
  • Expected Completion Date: 0
  • Actual Completion Date: 0
  • Source Data: RiP Project 41600

Subject/Index Terms

Filing Info

  • Accession Number: 01634649
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 03-133
  • Files: TRB, RiP
  • Created Date: May 12 2017 1:00AM