Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
Many regional and local governments across the United States (US), Europe, and Asia have inspection and maintenance (I/M) programs designed to reduce pollution from personal transportation. To test for a link between I/M and local air pollution levels, we estimate the contemporaneous effect of inspections on local air quality in the US state of California. We use day-to-day, within-county variation in the number of vehicles certified after failing an initial emissions inspection as a proxy for emissions-related repairs. Additional passed reinspections of older vehicles with inferior emissions technology (pre-1985 model year) reduce local carbon monoxide, nitrogen oxide, and particulate matter levels, but passed reinspections of newer vehicles with more modern engine technology have no economically significant effect on air pollution. This suggests that biannual emissions inspections as currently implemented will play less of a role in reducing local air pollution as polluting vehicles from the 1970s and 1980s leave the road.