As a group, young drivers have crash rates that far exceed those of older, experienced drivers. But even among teenagers there are age-related differences; crash rates decline consistently and dramatically with each yearly increase in age. A more precise understanding of how crash rates decline within the teenage group might provide insights into when experience is most influential. To address this issue, this study examines month-to-month changes in collisions among new drivers. It was found that crash rates drop most dramatically during the first 6 months of driving. Involvement in certain types of crashes-e.g. run-off-the-road, single-vehicle, night, weekend-declines more rapidly. The findings suggest that novices improve their driving in a relatively short period of time. A graduated driver licensing system is identified as an effective method for ensuring that this development takes place in a more forgiving environment.