Abstract
The proportion of heavy vehicles is one of the factors that can influence the operational performance of arterial road segments, particularly on corridors serving regional movements under heterogeneous traffic conditions. This study analyzes the sensitivity of average speed and average simulated delay to variations in heavy-vehicle (HV) proportion on National Road 1 in Astanajapura, Cirebon Regency, using PTV VISSIM microsimulation. Model inputs were obtained from geometric surveys, traffic counts, and speed observations during the selected peak hour. The baseline model was evaluated using the GEH statistic for traffic volume and MAPE for average speed, resulting in GEH values of 0.084 and 0.188 and MAPE values of 4.451% and 4.761% for Directions 1 and 2, respectively. The observed baseline HV proportions were 1.50% in Direction 1 and 1.84% in Direction 2. Five hypothetical scenarios were then evaluated at HV proportions of 5%, 10%, 15%, 20%, and 25%, while total traffic demand, road geometry, and calibrated driving-behavior settings were maintained across scenarios. The simulated results showed decreasing average speed and increasing average delay as the HV proportion increased. In Direction 2 toward Cirebon City, average speed decreased from 31.97 km/h under the baseline condition to 23.05 km/h at 25% HV, while average delay increased from 2.04 to 8.14 s/veh. Descriptive linear trend analysis, using the actual direction-specific baseline HV proportions together with the five hypothetical scenarios, indicated a stronger simulated response in Direction 2. These findings indicate that the operational performance of the modeled arterial segment is sensitive to changes in vehicle composition, particularly under the higher-volume traffic condition.