Since 2011, the National Association for Stock Car Auto Racing (NASCAR) has forced drivers to pick one of three national series for which they would be eligible to compete for a season championship. Prior to this "Pick-A-Series" rule, many drivers in the premier Sprint Cup Series competed regularly in the Nationwide Series, which is a developmental division for less experienced drivers. I examined whether the removal of moonlighting Sprint Cup drivers from championship contention encouraged less aggressive driving among those who competed exclusively in the Nationwide Series. There was weak evidence that the Pick-A-Series rule reduced accident proneness among Nationwide drivers relative to Sprint Cup drivers.