An Empirical Assessment of Traffic Volume Influence on Roadside NO₂ Concentration: A Micro-Scale Statistical Analysis in Makassar, Indonesia
Abstract
Rapid urban motorization in Makassar has intensified roadside exposure to traffic-related pollutants. This study empirically evaluates the direct statistical relationship between traffic volume and roadside nitrogen dioxide (NO2) concentration along a major arterial corridor. Field measurements were conducted during three time periods (morning, midday, and afternoon) on one representative weekday and one weekend day. Traffic volume was converted to Passenger Car Units (PCU), and NO2 concentration was measured using the Griess-Saltzman method in accordance with national standards. Pearson correlation and simple linear regression were applied to quantify the emission–concentration relationships at the microscale level. The results indicated a strong positive correlation between traffic volume and NO2 concentration (r = 0.874, p < 0.05), with traffic density explaining 76.3% of the variability in concentration (R2 = 0.763). Despite limited temporal coverage, the findings demonstrate that traffic congestion is a dominant determinant of short-term roadside NO2 accumulation. This study provides localized empirical evidence supporting traffic-based emission control strategies in emerging urban environments.