Intersection Design to Accommodate ADA Curb Ramps: Studies on Pedestrian Safety at Intersections

Porter, Dunn. This report presents a Safe System for Intersections (SSI) method that intersection planners and designers can readily implement, that dovetails with the typical U.S. project development process, and that uses commonly available projectlevel data. The SSI method is presented in the context of a Stage 1 Intersection Control Evaluation (ICE), at the scoping phase of project development where intersection alternatives are analyzed with respect to whether they meet project needs and are practical to pursue. The method incorporates concepts of conflict point identification and classification, exposure, kinetic energy transfer, conflict point severity, and intersection movement complexity. Application of the SSI method results in multiple measures of effectiveness (MOEs) and a set of SSI scores that characterize the extent to which an intersection alternative in a given context aligns with the principles of kinetic energy management and a Safe System. The SSI MOEs and SSI scores can serve as additional safety metrics to inform the process of screening alternatives and identifying an optimal solution for an intersection. The report includes an overview of Safe System concepts and principles, a detailed description of the SSI method, example project applications, and a future vision for the method.

Patil, Majumdar, Sahu. This study presents a methodology for evaluating a set of crash-prone sidewalk and crosswalk locations in an urban area with respect to their existing walkability condition and recommending improvement needs. Initially, a set of 15 sidewalk specific and 10 crosswalk specific attributes relevant to India were identified from the literature. Subsequently, the analytical hierarchy process was used to estimate relative weights associated with the attributes from the perspective of relevant experts. A weighted sum method was then used to formulate a Sidewalk Condition Index (SCI) and Crosswalk Condition Index (CCI) for evaluating the condition of the existing pedestrian sidewalks and crosswalk infrastructures. Ten locations across Hyderabad with the highest pedestrian fatalities during the last three calendar years were selected as study locations. The location specific SCI and CCI estimates were used to prioritize the locations with regard to their existing condition and infrastructural requirements. Results indicated that sidewalk attributes such as sidewalk lighting, cleanliness, physical separation of traffic, and traffic speed, and crosswalk attributes such as conflicts with crossing traffic, crosswalk illumination, and intersection control, influenced safety and walkability significantly. Measures such as the provision of exclusive right-of-way for pedestrians, maintaining the sidewalk quality, enforcing no jaywalking, re-design of signal timing with pedestrian phase, and provision of zebra crossings and refuge islands, would improve walkability at pedestrian crash-prone locations across Hyderabad. This proposed methodology and the research findings could act as a critical tool to improve the overall safety and walkability of sidewalks and crosswalks in Indian cities.

Kitleson & Assoc. This report provides specific guidance for four common Alternative Intersections and Interchanges (A.I.I.s): Diverging Diamond Interchange (DDI), Restricted Crossing U-Turn (RCUT), Median U-Turn (MUT), and Displaced Left-Turn (DLT). In addition, the guide provides a principles-based approach that is applicable to any A.I.I. or conventional intersection form, including new A.I.I. forms not yet developed. A central concern with A.I.I.s is how to provide information to pedestrians, bicyclists, and drivers about the direction of car traffic, pedestrian crossing, and bicycle facilities, particularly when those new intersection designs feature unfamiliar traffic flows and patterns. The concern is acute for visually impaired pedestrians, who require information about the alignment of crosswalks, signal controls, crossing times, direction of traffic, and direction through islands. The purpose of this guide is to help transportation practitioners improve and integrate pedestrian and bicycle safety considerations at A.I.I.s through planning, design, and operational treatments. The guide (1) identifies and evaluates current practices, and emerging technologies and trends, in the United States and internationally; (2) describes current best practices for measuring the effectiveness of such A.I.I. treatments; (3) evaluates the safety and operational outcomes of specific A.I.I. treatments; and (4) identifies and ranks treatments for typical types of projects.

Sanders, Schultheiss, et al. This report provides a process for selecting intersection designs and operational treatments that provide safety benefits for pedestrians and bicyclists, and the most appropriate situation for their application. The report draws from and builds on the strengths of key countermeasures and safety resources, tying these together in a systematic process for transportation practitioners to use to improve bicycle and pedestrian safety at intersections. The guide provides a step-by-step process for selecting intersection safety treatments based on site conditions, effectiveness, level of public process, and their potential to reduce certain common pedestrian and bicycle crash types. The appendix is a Countermeasure Glossary documenting 34 pedestrian and bicycle intersection safety countermeasures with two-page listings of key information for each.

Ashur, Alhassan, Designers and traffic engineers have to make decisions on selecting a pedestrian treatment whenever designing a new pedestrian facility or retrofitting an existing one. The goal is either to provide or improve pedestrian safety at pedestrian crossing facilities, including controlled locations of signalized intersections and approaches with stop and yield signs, and uncontrolled locations of intersections and midblock sites. Currently, the Indiana Department of Transportation (INDOT) has limited resources on pedestrian treatment selection that does not take into consideration key elements such as number of lanes and the existence of a raised median. Therefore, there is a need to find a more detailed and comprehensive approach to providing guidelines when deciding on a pedestrian crossing treatment. The approach has to be practical and can be easily utilized by traffic and design engineers, planners, and other constituents. Most of the State DOTs developed their guidelines on pedestrian crossing treatment based on several resources. However, the 2002 Federal Highway Administration FHWA-RD-01-075 study titled “Safety Effects of Marked Vs. Unmarked Crosswalks at Uncontrolled Locations” was adopted by several states either “as is,” with some modifications, or referenced as a source on pedestrian crosswalk selection. State DOTs mainly use standards and guidelines from the National Manual on Uniform Traffic Control Devices (MUTCD), Part 3 and National Cooperative Highway Research Program (NCHRP) Report 672 for roundabout crosswalk markings. In general, there are no clear warrants for grade separation treatment. In addition, there is a need for a national and comprehensive study to develop practical guidelines on pedestrian crossing treatments, especially on multilane roadways, complex intersections, and when the speed is 45 mph or more. This study proposed guidelines on crosswalk markings and treatment selection of pedestrian crossings based on a synthesis of federal and state reports, guidelines, design manuals, polices, and other relevant publications. It is recommended to adopt these guidelines as a reference for pedestrian treatment selection at INDOT. The results of a survey on pedestrian crossing treatments indicate that the most effective and most frequently used treatments by the different states represented in the survey are advanced signs, crosswalk signs and pavement markings, countdown displays at signalized intersections, curb extensions, high-visibility signs and markings, and median refuge islands. The least effective and least frequently used treatments are automated detection, in-roadway warning lights, overhead flashing beacons (passive), pedestrian crossing flags, pedestrian railings, and split midblock signals. In addition, the main recommendation on high-speed divided highway pedestrian crossings is to provide enough time for pedestrian to cross the entire width of the intersection without a median whenever there is a demand.

Candappa, Logan, et al. Fatal and serious injury crashes persist at intersections despite current efforts to address this. Little research specifically investigates the role played by existing intersection design in perpetuating serious intersection crash outcomes despite an increasing move to incorporate Safe System design on to roads. This paper identifies design principles deemed important to align intersection design with Safe System approaches, including exploring the impact of speed and angle on overall kinetic energy of a crash. Existing as well as new intersection designs are presented that are believed to incorporate the identified principles. An assessment is made of the alignment of the new and existing designs with the identified principles

Bonneson, Pratt, Songchitruksa. For intersections with a permissive or protected-permissive left-turn mode, pedestrians cross during the permissive period. This operation requires the left-turn driver to yield to both opposing vehicles and pedestrians, prior to accepting a gap and completing the turn. Pedestrian crash risks are increased in these complicated driving conditions because left-turn drivers sometimes fail to yield to pedestrians. This document summarizes the research conducted and the conclusions reached during the development of guidelines for pedestrian safety treatments at signalized intersections. The guidelines are focused on treatments that alleviate conflicts between left-turning vehicles and pedestrians. One treatment addressed in the document is the use of protected or protected-permissive left-turn operation. The guidelines are based on consideration of pedestrian safety and vehicle operation. These considerations include the road-user costs associated with pedestrian-vehicle crashes and vehicle delay. The guidelines were incorporated in the Traffic Signal Operations Handbook. The guidelines were also incorporated into a spreadsheet that was developed to accompany the Handbook. The Handbook was previously developed for Project 0-5629. It provides guidelines for timing traffic control signals at intersections that operate in isolation or as part of a coordinated signal system.

Salamati, Schroeder, et al. This paper describes the development and implementation of the conflict-based assessment of pedestrian safety (CAPS) methodology for the evaluation of pedestrian accessibility at complex intersections. Significant research has explored pedestrian access to modern roundabouts and other complex intersections, and a significant focus has been placed on accessibility for pedestrians who were blind. A majority of these studies relied on actual street crossings by study participants under the supervision of a trained orientation and mobility specialist. These crossing studies quantified risk from a measurement of intervention events, in which the orientation and mobility specialist had to physically stop the participant from crossing. Although such studies provide useful data on the crossing risk at a particular intersection, street crossings can be dangerous to the study participants and are time-consuming and expensive to conduct. The CAPS method emphasizes the use of conflict-based safety factors to quantify risk in a framework compatible with indicator studies. This method relates pedestrian crossing decisions to advanced measurements of vehicle dynamics to estimate lane-by-lane conflicts and identifies the grade of conflict on the basis of a five-criterion rating scale. The CAPS framework was applied to a study of crossings by blind pedestrians at a multilane roundabout. The resulting risk scores were calibrated from the actual orientation and mobility interventions observed during the study. The calibrated CAPS framework correctly matched all
(high-risk) orientation and mobility intervention events and further identified other (lower-risk) pedestrian–vehicle conflicts. The CAPS framework provides a more efficient, objective, and consistent safety assessment of pedestrian crossings in a research context, without the need for pedestrians to step into the roadway.

Brewer, Hawkins. This product is formatted as a chapter to be included in a current or future TxDOT manual. The chapter presents guidance on the use and placement of selected treatments to accommodate pedestrian accessibility at signalized intersections. Specific accommodations discussed in the chapter include curb ramps and blended transitions, accessible pedestrian signals, and countdown pedestrian signals.

Kim. Hunter. The Manual on Uniform Traffic Control Devices (MUTCD) contains the national standard for installing and maintaining traffic control devices on all streets and highways. The 2003 MUTCD contains numerous corrections, revisions, and updates to the millennium edition (2000). One update is related to the definition of crossing distance at signalized intersections, where the crossing distance is extended to the far-side curb rather than the center of the farthest traffic lane. This study investigated the sensitivity of intersection performance to crossing distance and walking speed, critical constraints in the determination of the minimum green time. Three crossing distance standards and four walking speeds are considered. With Highway Capacity Manual (HCM) procedures, the impacts of the given crossing distance definitions and walking speeds on intersection operations were tested on two intersection configurations over a range of cycle lengths and traffic volumes. The effect on intersection performance was found to be most significant at low cycle lengths, in some instances with the delay increased manyfold. However, when cycle lengths were increased to account for the pedestrian constraints, optimal delay rarely increased by more than a few seconds. Additionally, as the discrepancy between the critical lane traffic volume on the main and cross streets was increased, the impact of pedestrian green times on vehicle delay also increased. It was seen that as the cycle length increased, pedestrian minimum green times no longer governed, so the impact of pedestrians on intersection performance became increasingly insignificant, often with a minimal impact on the optimal performance.

Barlow, Franck. This article discusses the interactive nature of modern actuated intersections and the effect of that interface on pedestrians who are visually impaired. Information is provided about accessible pedestrian signals (APS), the role of blindness professionals in APS installation decisions, and techniques for crossing streets with APS.

Boodlal. FHWA-SA-03-01. In order to meet the needs of all sidewalk users, designers must have a clear understanding of the wide range of abilities that occur within the population. Sidewalks, like roadways, should be designed to serve all users. This includes children, older people, parents with strollers, pedestrians who have vision impairments, and people using wheelchairs and other assistive devices. Just as a roadway will not be designed for one type of vehicle, the design of sidewalks should not be limited to only a single type of pedestrian user. Because the side­walk is the basic unit of mobility within our overall system of transportation, every route and facility must be usable.

Sarkar. In the modal hierarchy, pedestrians "encased in soft exposing shell" are the most vulnerable when exposed to conflicts and barriers. In dense urban areas, where walking is an important mode to complete short trips, there is a continual need for evaluation of the existing roads and walkways, so that appropriate actions can be taken to eliminate or redress conditions that compromise pedestrians' safety. This paper proposes a method that would examine different facets of safety. The proposed method evaluates the existing design and conditions at two levels: first, at macrolevel (Service Levels A-F), and second, at microlevel [Quality of Service (QOS) Levels A-F]. Also discussed in this work are the methodologic processes for using the service and QOS levels, and the strengths and weaknesses of the method