Balancing emission reduction and regulatory burden under inspection limits for diesel fleets

Abstract

Effectively regulating in-use vehicle emissions requires methods that can identify high-impact emitters within heterogeneous vehicle fleets. This study develops a vehicle-level NOx accounting method based on inspection data, converting measured NOx concentrations into estimated emissions and aggregating these estimates to the fleet level. This approach enables fleet-scale emission accounting that explicitly reflects heterogeneity in both vehicle emission intensity and activity levels. In the study region, using a full-sample 2024 dataset, we assess fleet-level emission heterogeneity and reduction potential under alternative Inspection and Maintenance limits. We find that China V diesel trucks dominate fleet emissions due to their large population size and substantial vehicle activity. Furthermore, tightening the inspection limit reveals a trade-off between emission reduction benefits and compliance costs. The proposed NOx Reduction Effectiveness Index (NREI) identifies an optimal threshold range where emission reduction efficiency peaks, providing a scientific basis for balancing environmental benefits with maintenance burdens in policy optimization.