Coupled MOVES–AERMOD modeling and field validation of carbon monoxide dispersion from motorcycle-dominated traffic at a complex five-leg urban intersection in Makassar, Indonesia

Abstract

Urban intersections are major hotspots of traffic-related carbon monoxide (CO) pollution in rapidly growing cities.However, integrated emission-dispersion modeling studies with field validation remain limited in developing urban regions, particularly in Eastern Indonesia.This study aimed to simulate and validate CO dispersion at the Mandai Five-Leg Intersection, Makassar, using an integrated MOVES-AERMOD framework.Traffic data were collected through 12-hour classified traffic surveys and grouped into motorcycles, passenger vehicles, and heavyduty vehicles.Vehicular CO emissions were estimated using emission factors derived from the Motor Vehicle Emission Simulator (MOVES3), while atmospheric dispersion was simulated using AERMOD with site-specific meteorological data obtained from BMKG Region IV Makassar.Model performance was evaluated using field measurements at monitoring locations and statistical indicators including mean bias (MB), root mean square error (RMSE), and coefficient of determination (R²).The results showed that peak traffic occurred during the evening period (17:00-18:00 WITA), with motorcycle volume reaching 5,080 veh/h.Motorcycles were identified as the dominant emission source, contributing 39,457.06g/h of CO emissions.AERMOD simulations produced maximum CO concentrations of 83.2 µg/m³ for the 1-hour averaging period and 12.1 µg/m³ for the 24-hour averaging period near the intersection center.Validation results demonstrated strong agreement between observed and simulated concentrations (MB = 3.8 µg/m³, RMSE = 4.40 µg/m³, R² = 0.92).The study confirms that the integrated MOVES-AERMOD framework can reliably represent traffic-related CO dispersion and provides useful support for urban air quality management in rapidly urbanizing tropical cities.

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