There is increased interest by state and local transportation agencies as well as by the general public 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. According to the American Community Survey conducted by the U.S. Census Bureau, between 2007 and 2016 the average percentage of commuters who walk or bike increased from 2.5 to 2.8 and from 0.4 to 0.6 respectively (U.S. Census Bureau, Department of Commerce 2016). The 2009 National Household Travel Survey (NHTS) estimated 41 billion walking trips per year, accounting for 10.4% of all trips undertaken and bicycle trips increased from 0.7% of total trips in 1995 to 1.0% in 2009 (Federal Highway Administration 2011). These non-motorized trips, made by users of all ages and abilities, tend to be short and traverse signalized intersections in urban and rural settings. Signal timing is typically optimized for motor vehicles and delays at signalized intersections tend to affect pedestrians disproportionately compared to auto trips. The Highway Capacity Manual (HCM) states that delays greater than 30 seconds are associated with increased frustration and risky behaviors leading to pedestrian noncompliance which may lead to their injury or death. The delay experienced by non-motorized users at crossings may be due to many factors, including the traditional focus on prioritizing vehicular movement, geometric features/constraints, or other infrastructure related limitations at signalized intersections.
Research on pedestrian safety at intersections has focused on lack of driver yielding, pedestrian noncompliance, and pedestrian visibility. This has resulted in the emergence of countermeasures such as countdown pedestrian signals, enhanced beacons, leading pedestrian intervals, and exclusive pedestrian phasing. Although limited, bicycle safety research has focused on improving the safety of bicyclists in the traffic stream, focusing on design treatments rather than intersection operations with little research available on signal timing. Despite the availability of safety measures, due to slow technology transfer and assimilation or misapplication, current national trends show an increase in fatalities and injuries for these non-motorized users.
As the number of bicyclists and pedestrians increases, safety and operations at intersections remain a serious concern. Consequently, more comprehensive guidance related signal design and operations strategies is needed.
The objectives of this research are to (1) identify and evaluate a broad range of current international and national practices for signal design and operations strategies for non-motorized users including vulnerable road users with disabilities; (2) identify gaps in the state of practice on signalized intersections with multimodal specific infrastructure and intersections with varied geometric designs (e.g., signalized path crossings, diverging diamond interchanges, continuous flow intersections, etc.); (3) develop guidance for traffic signal design and operations strategies that will address the needs of non-motorized users and increase their respective multimodal connectivity; (4) develop a means to convey how to best incorporate findings to a wide range of stakeholders including those with visual impairments and other disabilities; (5) recommend germane language for inclusion in future updates to guidance documents (e.g., the AASHTO design manual, the Traffic Signal Timing Manual and specifications); and (6) identify opportunities for future research.