Understanding the Safety Impact of Protected Intersection Design Elements: A Driving Simulation Approach

• Published in: Transportation Research Record: Journal of the Transportation Research Board
• Main Authors: Deliali, Aikaterini, Campbell, Nicholas, Knodler, Michael, Christofa, Eleni
• Format: Article in Journal/Newspaper
• Language: English
• Published: SAGE Publications 2020
• Subjects: Mechanical Engineering; Civil and Structural Engineering; Refuge Island; Refuge Islands
• Online Access: http://dx.doi.org/10.1177/0361198120909382; http://journals.sagepub.com/doi/pdf/10.1177/0361198120909382; http://journals.sagepub.com/doi/full-xml/10.1177/0361198120909382

Protected intersections are used to facilitate safe crossings for non-motorized users. As a relatively new treatment in North America, it is essential to understand how their design elements, such as bicycle intersection-crossing pavement markings and corner refuge island size, enhance bicyclist safety. A driving simulation experiment was developed to test the effectiveness of different design elements of protected intersections on driver speeds. Participants were exposed to different protected intersection designs that varied with respect to the corner refuge island width and bicycle intersection-crossing pavement marking levels. Their speed at two parts of the right turn, that is, approach and curve speed, was analyzed. A combination of design elements, participant demographics, or bicyclist presence at the intersection affects driver behavior at a protected intersection. The results indicate that the presence of a bicyclist crossing a protected intersection significantly reduces speeds for drivers performing a right turn. Corner refuge islands with larger width were found to reduce speed at the curve as they were accompanied by larger curb extensions which essentially reduce the space for the automobiles. Bicycle intersection-crossing pavement markings influenced only approach speeds prior to the actual turn since that is the location where they were the most visible. Age, gender, and bicycling frequency were observed to affect turning speeds, indicating that design elements alone cannot determine the safety effectiveness of a protected intersection. The findings of this study can guide the implementation of protected intersections.