Understanding Vulnerable Road User Behavior and Perceptions Through Heart Rate Data: An Evaluation of Roadway Design Alternatives Through In-Lab and In-Field Case Studies

Cyclists and pedestrians represent some of the most vulnerable users (VRUs) of roadway infrastructures. Understanding their behaviors, preferences, and interactions with the environment is critical in order to aid planners, engineers, and decision-makers to promote safer spaces and active mobility. This research presents two case studies in which VRUs’ behaviors and their interactions with the built environment were tested with the aid of virtual reality (VR) simulation and wearable sensors for heart rate (HR) data collection, in both in-lab and real-world settings.
The first part of this thesis presents a novel way of studying cyclists’ perceptions of bicycle infrastructure design alternatives in a safe and low-cost way using immersive virtual environments modeled after a real-world corridor and a previously validated bike simulator. Three infrastructure
scenarios were tested: sharrows, a separated bike lane, and a protected bike lane with flexible delineators. Results of the used multinomial logit model suggest gender, age, and abrupt changes in HR affect cyclists’ preferences for bike infrastructure design. Overall, gender emerges as the most practically significant predictor variable for bicycle infrastructure preference, with men more likely to prefer sharrows and women more likely to prefer protected bike lanes. Exploratory analysis also suggests that bicyclists who self-identified as “strong and fearless” are more likely to choose sharrows as the preferred design, while bicyclists who self-identified as “interested but concerned” more often chose the protected bike lane. These results highlight the importance of understanding preferences of not just current cyclists, but potential future cyclists. VR simulation offers a low-cost, safe, and efficient method to understand the preferences of individuals interested but not yet choosing cycling as a mode.
The second part of this thesis presents the experimental design and findings of a pilot naturalistic pedestrian experiment conducted on the main commercial street in Staunton, Virginia. The experiment was designed to measure variations in the pedestrian experience when the corridor is open and closed to vehicular traffic, a distinct opportunity provided by a local initiative to repurpose the corridor. Smart eyeglasses with eye-tracking technology enabled the analysis of pedestrians’ gaze, while a smartwatch collecting HR data was used to identify potentially stressful events or stimuli, allowing researchers to retrieve information from the pedestrian perspective. Results show that most of the abrupt changes in HR occur while participants focus their attention on the ground of their walking route and at locations near intersections. This study sets the groundwork for future research on linkages between the experiential dimensions of the urban environment and pedestrian behaviors and physiological reactions.
Through these two case studies, this thesis seeks to add to the limited existing literature related to understanding VRUs’ behavior and perception using physiological data, in different infrastructure design contexts. The thesis identifies the value of low-cost wearable sensor technology as well as the challenges with implementing such sensors, both in in-lab and in-field settings, with cyclists and pedestrians.