Technology and the Effectiveness of Regulatory Programs Over Time - Vehicle Emissions and Smog Checks with a Changing Fleet

Sep 15, 2026

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Personal automobile emissions drive major urban air pollution, prompting inspection and maintenance (I/M) programs worldwide. Empirical evidence on whether mandated inspections and repairs reduce local air pollution is limited. This study estimates the contemporaneous effects of inspections in California using within-county day-to-day variation in repairs and re-certifications after failing initial emissions tests (1998–2012). Re-inspections lower carbon monoxide, nitrogen oxide, and particulates for older, pre-1985 vehicles, while newer vehicle re-inspections show no economically significant impact. Results also indicate station quality matters for older-vehicle re-inspections, with limited effects on ambient ozone.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages58

Reading Time2 h 26 min

AccessFree to download

Introduction

Study approach and data

Main findings on vehicle age and pollutant effects

Station quality and ozone results

Technology and the E􀀋ectiveness of Regulatory Programs Over Time: Vehicle Emissions and Smog Checks with a Changing Fleet Nicholas J. Sanders and Ryan Sandler 􀀃 December 14, 2018 Abstract Personal automobile emissions are a major source of urban air pollution. 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. But there is little empirical evidence directly linking mandated inspections, maintenance, and local air pollution levels. To test for a link, we estimate the contemporaneous e􀀋ect 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 repaired and re-certi􀀌ed after failing an initial emissions inspection, with individual-level data from 1998{2012 from California's inspection program. Additional re-inspections of older vehicles with inferior emissions technology (pre-1985 model year) reduce local carbon monoxide, nitrogen oxide, and particulate matter levels, while re-inspections of newer vehicles with more modern engine technology have no economically signi􀀌cant e􀀋ect on air pollution. This suggests emissions inspections have become less e􀀋ective at reducing local air pollution as more highpolluting vehicles from the 1970s and 1980s leave the road, and provides an example of how the social e􀀎ciency of programs can change under improving technologies. We also estimate the importance of station quality, using a metric devised for California's new STAR certi􀀌cation program. We show re-inspections of older vehicles conducted by low quality inspection stations do not change air pollution, while inspections at high quality stations have a moderate e􀀋ect on pollution concentrations, which suggests the potential for ine􀀋ective monitoring at low quality inspection stations. We 􀀌nd little e􀀋ect on ambient ozone levels, regardless of station quality or vehicle age. 􀀃 Sanders: Cornell University and NBER, [njsanders@cornell.edu](njsanders@cornell.edu). Sandler: Bureau of Consumer Financial Protection, [ryan.sandler@cfpb.gov. We are](ryan.sandler@cfpb.gov. We are) grateful to Dan Hosken, Mark Jacobsen, Thomas Koch, Devesh Raval, Joseph Shapiro and participants in the Economics Brownbag at the Federal Trade Commission for helpful comments and suggestions. Any opinions in this paper are those of the authors and do not necessarily re􀀍ect those of the Bureau of Consumer Financial Protection or the United States. 1 Introduction Automobile pollution has substantial impacts on health, and regulating ambient air pollution from automobile tra􀀎c is a public concern throughout the world.1 Despite regulatory advancements and improvements in engine technology, motor vehicles remain responsible for 75% of carbon monoxide (CO) emissions in the United States, and over 50% of nitrogen oxide (NOx ) emissions.2 Governments in both developed and developing countries have tried a number of policies to reduce pollution from personal automobiles. Improving fuel standards can decrease emissions per mile driven, but such programs disproportionally impact low-income households and decrease average road safety (Jacobsen, 2013a,b) . Driving restriction programs have varied success rates when it comes to actually reducing local pollution (Davis, 2008; Wol􀀋, 2014; Simeonova et al., 2018) . Scrappage programs, often referred to as \Cash for Clunkers," can directly remove the dirtiest vehicles from the road, but recent work shows that such programs have substantial problems with adverse selection and may only slightly shift forward the timing of vehicle replacement (Sandler, 2012; Mian and Su􀀌, 2012; Li et al., 2013; Hoekstra et al., 2014) . Inspection and maintenance programs (I/M), the focus of this paper, attempt to limit tailpipe emissions through regular inspections and repairs, without changing driving behavior or 􀀍eet compositi

FAQs

What question does the paper examine about inspection and maintenance (I/M) programs?

Whether mandated vehicle inspections and subsequent repairs causally reduce local air pollution levels in practice.

How does vehicle model year affect the paper’s findings on pollution reductions?

Re-inspections of older vehicles (pre-1985) reduce local pollutants, while re-inspections of newer vehicles show no economically significant effect.

What role does inspection station quality play in the results?

Older-vehicle re-inspections at low-quality stations do not change air pollution, whereas inspections at high-quality stations have a moderate effect on pollution concentrations.

Sep 15, 2026

Uploaded by Ivy