Multiclass Traffic Flow Dynamics: An Endogenous Model

Vehicles on roads can be distinguished, each defined by its own set of properties (e.g., fleet length and free-flow speed). The traffic states on roads can be attributed to the longitudinal heterogeneity in vehicles. Vehicles slower than prevailing vehicles are defined as moving bottlenecks. On a multilane road section with multiple vehicle types, slower vehicles create moving bottlenecks and induce overtaking by faster vehicles so as to maintain their higher desired speed. The influence of single-class moving bottlenecks has been studied in the past. However, the impacts of multiple classes of moving bottlenecks have not yet been fully explored. This paper categorizes vehicles into passenger cars, medium trucks, and heavy trucks. By defining medium trucks and heavy trucks as moving bottlenecks, we develop analytical formulas for the fundamental diagram on a multilane road section with heterogeneous moving bottlenecks. The formula confirms that the composition of traffic and the longest truck platoon length influence the fundamental diagram. We then conduct simulations using a first-order kinematic wave model in Lagrangian coordinates to validate the fundamental diagram developed with the analytical formula and obtain promising results. This study provides fundamental knowledge for multiclass traffic modeling and multilane traffic operations.

Investigation of Flood Routing Using Variable Parameter Kinematic Wave Model (VPKWM) for Non-Prismatic Natural Channel in an Ungauged Basin

This research concerns about the development and application of Variable Parameter Kinematic Wave Numerical model (VPKWM) based on 1-D Saint-Venant equation, to study the behaviour of the propagation of a flood wave in Non-prismatic natural waterways in an ungauged basin. The channel slope and wetted perimeter are considered as variable because of the irregularity of the boundary of the channel and the change in magnitude of discharge. The scarcity of reliable inflow data at upstream is a serious problem for the flood routing process in an ungauged basin. In this study the inflow hydrograph and lateral inflow hydrographs are obtained using SCS-CN method as rainfall runoff model. The performance of the model assessed considering four parameters such as root mean square error (RMSE), peak discharge, peak time and total volume. The results indicated that the VPKWM for non-prismatic channel provided reasonable output compared with the observed data.

Assessing the Influence of Cell Size on Flood Modelling by the PWRI-DH Model Using IFA

When modeling by IFAS it becomes necessary not only to obtain the model parameters but also to define the cell size, which influences both the tank model and the kinematic wave model. Since PWRI-DH model, the model in which is based IFAS, is a distributed model, the cell size defines the discretization of the computational domain. On the other hand, PWRI-DH model use altitude data such as GTOPO30 and Hydro1k, both with resolution of 1 km and IFAS is restricted to a minimum cell size of 100 m. Because of the restriction on cell sizes, an error on the predicted discharge is obtained, since this size of cell is not small enough to capture any details. As results, it is necessary to find a cell size able to predict discharge correctly, and more important, to quantify the error produce by the model and taking it into account in the analysis of the results. In this paper, an analysis of the influence of cell size on the IFAS predicted discharge is performed. The effect of cell size on the delimitation of the river as well on the definition of the land use, on the definition of the vegetation cover, on the definition of the topographic of the river basin is evaluated in detail. From the results of this study, the authors have been able to improve the accuracy of the PWRI-DH model and therefore to predict discharge using IFAS, more accurately. Finally, conclusions of this study are presented.