An Analysis of the Relationship between Casualty Risk Per Crash and Vehicle Mass and Footprint for Model Year 2000-2007 Light-Duty Vehicles

National Laboratory is an equal opportunity employer. i Acknowledgements We would like to thank those who reviewed earlier drafts of this report, and provided helpful comments and insights: ii iii Executive Summary NHTSA recently completed a logistic regression analysis (Kahane 2012) updating its 2003 and 2010 studies of the relationship between vehicle mass and US fatality risk per vehicle mile traveled (VMT). The new study updates the previous analyses in several ways: updated FARS data for 2002 to 2008 involving MY00 to MY07 vehicles are used; induced exposure data from police reported crashes in several additional states are added; a new vehicle category for car-based crossover utility vehicles (CUVs) and minivans is created; crashes with other light-duty vehicles are divided into two groups based on the crash partner vehicle's weight, and a category for all other fatal crashes is added; and new control variables for new safety technologies and designs, such as electronic stability controls (ESC), side airbags, and methods to meet voluntary agreement to improve light truck compatibility with cars, are included. In a companion report (Wenzel 2012b), we use the updated databases NHTSA has created to replicate their findings on the relationship between vehicle weight, size (actually footprint, or vehicle wheelbase times track width), and US fatality risk per vehicle miles traveled (VMT), for model year 2000 to 2007 light-duty vehicles involved in fatal crashes between 2002 and 2008. The data are examined in slightly different ways, to get a deeper understanding of the relationship between reductions in vehicle mass and footprint, and overall safety. This report compares the logistic regression results of the NHTSA analysis of US fatality risk per VMT with an analysis of 13-state fatality risk and casualty risk per crash. This final report incorporates revisions from the preliminary report released in November 2011, including revised estimates of national weights for vehicle miles traveled, inclusion of 2008 police-reported crash data from eight additional states, and responses to reviewers' comments. Our analysis differs from the NHTSA analysis in two respects: first, it analyzes risk per crash, using data on all police-reported crashes from thirteen states, rather than risk per estimated VMT; and second, it analyzes casualty (fatality plus serious injury) risk, as opposed to just fatality risk. There are several good reasons to investigate the effect of mass and footprint reduction on casualty risk per crash. First, risk per VMT, includes two effects that influence whether …