Adjusted saturation flow of some signalized intersection in Semarang, Indonesia

Indonesian Highway Capacity Manual or IHCM (1997) is a manual used to analyse performance of Indonesia's road network. It has been more than 20 years since the manual is firstly published, so that some parameters such as passenger car equivalent (pce) and base saturation flow (S₀) are no longer in accordance with actual conditions, which is indicated by significant differences between IHCM analysis results and empirical data. Several studies have been conducted in many cities and rural areas across Indonesia to explore pce, base saturation flow or other adjustment factors, in order to update IHCM, so in general, this manual will be more appropriate for current traffic conditions. This study is aimed at obtaining adjusted saturation flow from three signalized intersections in Semarang City, based on a comparison between predicted queue lengths and the empirical ones. Using the vehicle departure time slice data for green time, the pce and saturation flow was adjusted using regression method. Adjusted saturation flow at the observed intersection can be simplified in equation S = 506.48 We + 1857.9. Addition of variables still needs to be considered to gain a more general equation.