Over the last twenty years, large improvements in occupant safety have been made in NASCAR®'s (National Association for Stock Car Auto Racing, Inc.) racing series. While proper occupant protection requires both occupant restraint and preservation of sufficient occupant survival space, this study is focused mainly on the latter of these two necessities. The NASCAR tubular vehicle chassis has evolved through the years to provide improved protection for the driver in rollover incidents. The chassis has continued to progress over time to improve its strength as unique crashes sometimes highlighted opportunities for advancement. Recent enhancements tested using computer modeling, quasi-static testing, and full scale drop tests have improved the roof structure of the stock car chassis. These improvements have been incorporated into the 2013 NASCAR Sprint Cup and Nationwide Series cars.