Safety in Numbers: A Literature Review
In the context of pedestrian and bicyclist safety, the theory of Jacobsen’s 2003 “ Safety in Numbers” (SIN) posits an inverse relationship between the extent of walking and bicycling and the probability of motorist collisions with pedestrians and bicyclists. A literature review was conducted to summarize the state of research on SIN and identify potential implications of the work. The review chronologically describes research developing the SIN concept and subsequent work testing and expanding the theory. The literature review considers fields of study and areas of practice including engineering, planning and land use, sociology, psychology, education, public health, enforcement, human factors, and others. This breadth was especially important due to the broad target audience of this report who may apply the literature review results to their own future practice. These include State Highway Safety Offices, national organizations interested in the SIN topic, constituents from the Federal Highway Administration, planners, engineers, educators, advocacy groups, policymakers, State DOTs, metropolitan planning organizations, and roadway users — motorists, pedestrians, bicyclists — and law enforcement professionals.
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