Connecting Pedestrians with Disabilities to Adaptive Signal Control for Safe Intersection Crossing and Enhanced Mobility: Final Report
Technologies that connect pedestrians to intersections equipped with adaptive signal control allow the traffic signal system to communicate to pedestrians when it is safe to cross the intersection. This study developed a prototype mobile app for pedestrians with disabilities that interacts with the traffic signal system to communicate crossing intent to eliminate the need to seek out and push a pedestrian call button as well as personalized crossing constraints to ensure sufficient crossing time. This two-year study had three phases. In phase one, user needs were identified by conducting a workshop with more than 20 members of the local disability community, and the concepts of operations and system requirements were defined. In phase two, the prototype system was developed involving two subsystems, namely the pedestrian subsystem comprised of the mobile app, and the intersection subsystem, comprised of the adaptive traffic control system and other accompanying devices that enable communication between infrastructure and the mobile app. In phase three, field tests were conducted to evaluate and refine the developed app. Preliminary field tests were conducted in year one at the intersection of Centre Avenue and Cypress Avenue in Pittsburgh, Pennsylvania with 12 people with disabilities. Two surveys (before and after the field test) were distributed to understand specific user needs and challenges. Field tests were also conducted during year two at four intersections in the vicinity of Centre and Cypress Avenue with 14 people with disabilities. The app was evaluated during the period between August 16, 2019 and September 11, 2019.
Lessons learned were summarized from the study based on the practical challenges of the participants. According to the pedestrian’s type of disability, different limitations and challenges were observed.
- Supplement mobile pedestrian apps with stationary Bluetooth beacons. The earlier version of the app required the user to tap “start crossing” and “crossing completion” buttons at the beginning and end of each cross, which was reported as a problem for the participants. As a result, four Bluetooth beacons were installed at the test intersections, which provided reliable identification and enhanced overall localization, and thereby automating the detection of crossing start and end requests.
- Understand the limitations of complex intersections with many different signal phases in a cycle. Numerous signal phases were confusing to pedestrians with disabilities such as crossing when vehicles were permitted to turn left. Blind pedestrians, for example, with little to no familiarity of the intersection’s geometry had difficulty in locating the crosswalk. In addition, pedestrians must be warned when veering outside during crossings, particularly when crossing alone. Respondents mentioned implementing veer detection would be useful for the developed app.
- Consider implementing an auditory device at an intersection that announces when to cross. Such a feature would help determine when it was safe to cross especially when the individual was unable to listen to the sound of vehicular traffic, or if the traffic was very light. Visually impaired individuals found the app to have useful and clear auditory output. Participants also suggested including interaction with the app through voice commands. This would help provide more detail on the signal phasing and time to cross.
- Create an app that does not rely on additional equipment. Individuals responded that operating without an additional device needed to communicate with the infrastructure (i.e., the Dedicated Short-Range Communication sleeve) was useful. The newest version of the app used a cellular communication option (e.g. 3G/4G) to interact with the intersection and traffic signal control system.
- Alert pedestrians on the red signal phasing and/or emergency vehicles approaching the intersection. Providing a countdown for the red light as well as for the time remaining during the crossing phase would be useful for pedestrians with disabilities. The participants in this study mentioned that providing an indication to alert pedestrians when emergency vehicles were approaching is also desired.
- Integrate existing navigation and wayfinding apps to provide a more comprehensive intersection crossing experience. The current version of the app provides a “route following” feature that utilizes a user route, specified as a sequence of intersection corner waypoints. This information could be imported from popular apps used by individuals with disabilities. Such path information could be used to communicate the user’s expected arrival time to the next intersection in advance and allow the signal controller to factor this information into its real-time optimization of the intersection’s signal timing plan to streamline the user’s wait time before crossing the intersection.