Kai Funahashi

Publication Date


Document Type


First Advisor

Ashley, Walker S.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Geographic and Atmospheric Sciences


Geography; Meteorology


Motor vehicle accident research has focused primarily on macroscale assessments of traffic accident occurrence and the unsafe behaviors affiliated with drivers. Additionally, while the relationship between weather and traffic volume and the relationship between weather and traffic accidents have been analyzed separately, the connection of weather and traffic volume on traffic accidents has not been quantitatively appraised. This research uses the northeast Illinois region---an area with a diverse roadway system within rural agricultural expanses, vast suburban development, and the densely populated Chicago and Rockford urban cores---to determine the relationship of fatal and nonfatal traffic accident occurrence as a function of both hourly traffic volume and hourly snowfall rates. Specifically, is there a higher occurrence for traffic accidents during weak snow events than during heavy snow events? If so, is this a manifestation of the weather itself, of different traffic volumes during different snow intensities, or both? Accounting for traffic volume and weather can be difficult without normalizing for the number of snow events that occur. Results reveal a positive relationship between accident frequency and snowfall rates for damage-only and injury-only accidents, but the relationship fluctuates for fatal accidents and seems to diverge from a linear relationship. Additionally, there is a statistically significant difference in the daily total number of accidents between days with many weather-related accidents and few weather-related accidents. However, contrary to prior research, even though the relationship between snowfall rates and accidents was evident for the hourly frequency of damage-only and injury-only accidents per event, no relationship was discernible for the hourly frequency of fatal accidents per event. Part of the reasoning behind the discrepancy in the results of this research and that of prior efforts lies in the unique nature of the methods employed as this work attempts to subjectively account for the number of snow events. The methodology introduced could be used for other spatiotemporal domains and improved upon for future studies relating traffic accident frequencies per event.


Advisors: Walker S. Ashley.||Committee members: David Changnon; Xuwei Chen.||Includes illustrations and maps.||Includes bibliographical references.


75 pages




Northern Illinois University

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