Modeling speed-density, flow-speed, and flow-density relationships at Jakarta freeways

KURNIAWAN, Yusrizal, Prof. Dr. Ir. Siti Malkhamah, M.Sc

2009 | Tesis | S2 Magister Sistem dan Teknik Transportasi

High population growth, rapid expansion of social and economic activities, and motorization, affect DKI Jakarta road networks including the inner city freeways namely: Jakarta Intra Urban Toll Road (JIUT). Traffic conditions at JIUT corridors have been getting worse particularly in peak-hours. It is important to carry out freeway performance measures to give the information for the users (travellers) and the toll road operator regarding the existing situation in DKI Jakarta. To evaluate the traffic performance, it is important to know the characteristic of traffic parameters (flow, speed, and density) and the relationships among them. Research has been carried out aiming at modeling traffic parameters at Jakarta freeways based on traffic measurement. Conducted at Wiyoto Wijono corridors, traffic studies were carried out on four basic freeway segment locations in two directions. These studies comprised volume studies and speed studies, Furthermore, the studies classified vehicles into six types and conducted during twelve hours from 06.00 AM until 06.00 PM. Based on the field measurement data, the mathematic models of flow, speed and density relationships were developed. The research concluded that the Underwood model was the best approach due to the dynamic traffic of Wiyoto Wijono corridors. The relationships of Speed-Density, Flow-Speed and Flow-Density were established; i.e. S = 86.1690.e-0.0118.D, Q = 376.2561.S – 84.4322.S.Ln(S), Q = 86.1690.D.e-0.0118.D, respectively. Implementing the models, the traffic indicators (v/c, speed and density) showed that Pedati segments were the worst performance. The models showed that the capacity of freeways to be higher than the capacities predicted by IHCM (DGH, 1997) and HCM 2000 (TRB, 2000), i.e. 2676 pcu/lane-hour, compared to 2208 pcu/lane-hour and 2250 pcu/lane-hour respectively. It was also found that the optimum speed (leading to maximum traffic flow) was 32 km/h, the critical density was 84 pcu/km/lane and the minimum headway (when the flow reached its capacity) was 1.35 seconds.

Kata Kunci : freeway, traffic performance, flow, speed, density, v/c, headway