John Bigham

Geocoding police collision report data from California: a comprehensive approach.

BackgroundCollision geocoding is the process of assigning geographic descriptors, usually latitude and longitude coordinates, to a traffic collision record. On California police reports, relative collision location is recorded using a highway postmile marker or a street intersection. The objective of this study was to create a geocoded database of all police-reported, fatal and severe injury collisions in the California Statewide Integrated Traffic Records System (SWITRS) for years 1997-2006 for use by public agencies.ResultsGeocoding was completed with a multi-step process. First, pre-processing was performed using a scripting language to clean and standardize street name information. A state highway network with postmile values was then created using a custom tool written in Visual Basic for Applications (VBA) in ArcGIS software. Custom VBA functionality was also used to incorporate the offset direction and distance. Intersection and address geocoding was performed using ArcGIS, StreetMap Pro 2003 digital street network, and Google Earth Pro. A total of 142,007 fatal and severe injury collisions were identified in SWITRS. The geocoding match rate was 99.8% for postmile-coded collisions and 86% for intersection-coded collisions. The overall match rate was 91%.ConclusionsThe availability of geocoded collision data will be beneficial to clinicians, researchers, policymakers, and practitioners in the fields of traffic safety and public health. Potential uses of the data include studies of collision clustering on the highway system, examinations of the associations between collision occurrence and a variety of variables on environmental and social characteristics, including housing and personal demographics, alcohol outlets, schools, and parks. The ability to build maps may be useful in research planning and conduct and in the delivery of information to both technical and non-technical audiences.

Modeling Bicycle Passing Maneuvers on Multilane Separated Bicycle Paths

AbstractBicycle passing maneuvers represent interferences between bicycle travelers and are important operational attributes of bicycle traffic. The number of bicycle passing maneuvers has been used to evaluate the level of service (LOS) of off-street bicycle facilities. The primary objectives of this paper are to propose a method to model bicycle passing maneuvers on multilane bicycle paths with heavy bicycle traffic and explore the characteristics of those passes. The authors classified bicycle passing maneuvers into free, adjacent, and delayed passes according to the lateral distance between bicyclists during the passing. Models were developed to estimate the number of each type of passing maneuver on unidirectional two-, three- and four-lane bicycle paths. The authors used field observations of bicycle traffic on bicycle paths in Nanjing, China to calibrate and validate these models. The model predictions on bicycle passing maneuvers were consistent with the observations. The model sensitivity analyse...

Examining Long-Term Impact of California Safe Routes to School Program: Ten Years Later

California was the first state to legislate a Safe Routes to School (SR2S) program under Assembly Bill 1475 (1999). SR2S funds construction projects that make it safer for children to walk or bicycle to school and encourages a greater number of children to choose these modes of travel for the school commute. The main goal of this project was to assess the long-term impact of program-funded engineering modifications on walking and bicycling levels and safety. Improvements were evaluated with a targeted method to determine the countermeasures that resulted in safety and mode shift. The major results indicated that the safety of pedestrians increased within 250 ft of an infrastructure improvement, such as a sidewalk. There was also evidence of mode shift near improvements. Positive results for safety and mobility, as well as improved data collection for funded programs, should make SR2S programs competitive among other transportation needs.

Spatiotemporal Analysis of Macroscopic Patterns of Urbanization and Traffic Safety Case Study in Sacramento County, California

This study provides a preliminary investigation into the relationship between urbanization and traffic collisions by analyzing the spatial patterns in Sacramento County, California, from 1998 to 2008 through use of urban land classifications and traffic collision data. The ArcGIS directional distribution tool was used to create standard deviational ellipses to investigate the distributional trend of urban land and traffic collisions over time. Statistical outputs representing changes of geographical centroids, elliptical areas, and standard distances (long and short axes) were then compared. Collisions were also divided into subsets by severity level to account for inherent differences in the spatial distribution of different types of collisions. The results provided insight into the macroscopic spatial patterns of urban land and traffic safety and their relationships. The limitations of the method and the need for further research were discussed. The approach in this study would be useful for other metropolitan areas with similarly changing development patterns and can be helpful in guiding future research that compares these two phenomena.