Researchers have long recognized the importance of psychological processes in motor vehicle safety, but ecological theory-based research on factors that might contribute to motor vehicle crashes has lagged. This study was designed to test factors that might influence motor vehicle drivers' judgments of passability and fit-ability affordances. In particular, the authors tested personality and behavioral reinforcement as factors that might influence automobile drivers' judgments of affordances in three tasks set at various π-numbers: driving forward through a gap, driving backward through a gap, and fitting into a parallel-parking spot. Results across two studies suggest that personality does not relate to judgment of driving environment affordances, but institution of a behavioral reward system causes drivers to judge affordances in different ways. Implications for future research and for automobile safety intervention are discussed. Copyright © 2007, Lawrence Erlbaum Associates, Inc.