Are Neighborhood Bicycle Greenways the Answer? Analyzing the Impact of Bicycle Greenways on Collisions between Bicycles and Motor Vehicles

Abstract

With the population of urban areas growing at a rapid pace, cities are turning to new methods to manage the increased demand placed on space in the roadway. This increased demand carries the unfortunate side effect of bringing greater numbers of people into conflict while operating in traffic, and increases exposure to risk of collision overall. In the current version of the Seattle Bicycle Master Plan, Seattle Department of Transportation is turning to neighborhood bicycle greenways as a major tool to encourage more people to ride a bicycle as a primary mode of transportation – planning to increase the lane miles of neighborhood greenway to comprise 41% of the entire bicycle network at the completion of the Bicycle Master Plan. This thesis examines the role that neighborhood greenways play in relation to other bicycle facilities and asks: how do neighborhood greenways influence the likelihood of collisions between bicycles and motor vehicles? In order to find an answer to this question, I performed a linear regression analysis examining the relationship between bicycle-motor vehicle collision incidents in Seattle and average traffic volumes, lane miles of arterials, and proportions of bicycle facilities in the roadway. Although my model was unable to identify all of the factors that would predict bicycle-motor vehicle collision incidents, I found that average traffic volumes showed a significant positive correlation with bicycle-motor vehicle collisions, and that non-arterial local streets showed a significant negative correlation. As non-arterial streets are the exclusive domain of neighborhood bicycle greenways, I recommend that Seattle Department of Transportation accelerate the construction and designation of neighborhood greenways; establish a low-barrier method for bicycle riders to report bicycle-motor vehicle collision incident data to the City of Seattle, and; conduct a more thorough average count of bicycle rider traffic volumes across Seattle for improved analysis of bicycle rider safety in the future.