Future emission projections for light-duty vehicles in Korea: Integrating emission regulations, fleet transition, real-world vehicle performance, and link-level traffic activity.

This study presents a national-scale framework for projecting future light-duty vehicle emissions by integrating real-world emission performance, regulatory change, fleet transition, and link-level traffic activity, where a link represents the minimum unit of road classification. Using real driving emission data from 179 light-duty vehicles, Korea-specific operating mode-based emission factors for CO2, NOx, and CO were developed as functions of vehicle-specific power and speed. When combined with nationwide link-level activity data, these factors enable future emission projections that better reflect real-world driving conditions than conventional average-speed or aggregate-activity approaches. To examine fleet-transition effects, one baseline scenario and three accelerated internal combustion engine vehicle (ICEV) phase-out scenarios were considered. Results showed that, under the baseline scenario, 2050 emissions decreased by 64.9% for CO2, 72.1% for CO, and 98.8% for NOx relative to 2019. The moderate, strong, and aggressive transition scenarios further reduced cumulative CO2 emissions by 15.7%, 24.8%, and 30.2%, respectively, compared with the baseline, whereas additional NOx reductions were limited to about 2-4%. These findings indicate that pollutant control and CO2 mitigation follow different pathways: NOx reductions are driven mainly by stricter emission standards and fleet turnover, whereas substantial long-term CO2 reduction depends more strongly on accelerated ICEV phase-out.