Application of the Greenshield, Greenberg, Underwood, and Bell Models in Evaluating the Capacity of the Lembar Highway Segment (Rural Road) With Comparison to PKJI 2023

Road capacity evaluation is essential for maintaining efficient traffic operations, particularly on strategic transportation corridors experiencing continuous traffic growth. The Lembar Highway in West Lombok serves as a major access route connecting regional areas with Lembar Port, resulting in high traffic intensity and varying traffic characteristics influenced by roadside activities. This study aimed to determine the most appropriate macroscopic traffic flow model for evaluating the relationship between traffic speed, density, and volume on the Lembar Highway and to compare the estimated maximum traffic volume with the road capacity calculated using the Indonesian Road Capacity Guidelines (PKJI) 2023. The research employed a quantitative field survey conducted on three road segments. Traffic volume, speed, and geometric road data were collected from 06:00 to 18:00 WITA at 15-minute intervals. Traffic flow characteristics were analyzed using the Greenshield, Greenberg, Underwood, and Bell models, and model performance was evaluated based on correlation and determination coefficients. The findings indicate that the Greenshield model provides the best representation of traffic flow across all three segments, with correlation coefficients of 0.9051, 0.8435, and 0.8607, respectively. The estimated maximum traffic volumes were 2,276.403, 3,111.682, and 2,465.361 passenger car units per hour, all of which remained below the corresponding PKJI 2023 road capacities. These results demonstrate that the existing road sections are still capable of accommodating current traffic demand. Therefore, the Greenshield model is recommended as the most suitable approach for evaluating traffic flow characteristics and supporting road capacity assessment on the Lembar Highway.