Comments on the Joint Proposed Rulemaking to Establish Light- Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy Standards Docket No. NHTSA–2009–0059 and

Pinpointing the causes of a vehicle crash, and any fatalities or serious injuries that occur incrashes, is a very difficult task. Many variables can contribute to one vehicle model having ahigher risk on-road risk than another model; these variables can be grouped into three generalcategories, driver characteristics and behavior, vehicle attributes and condition, and crashlocation and environment.The 2003 NHTSA study (Kahane, 2003) did a thorough job accounting for many of the variablesthat may affect injury and fatality outcomes in crashes. However, even this comprehensiveanalysis did not account for all of these variables; indeed, it may not be possible to fully accountfor all of the important variables that determine crash outcomes. I have critiqued this analysis incomments submitted for previous NHTSA rulemakings (Wenzel and Ross, 2004a; Wenzel andRoss, 2004b; Wenzel and Ross, 2005; Wenzel and Ross, 2008).