Kasun Wijayaratna

Integrating the Bus Vehicle Class Into the Cell Transmission Model

The traditional cell transmission model (CTM), a well-known dynamic traffic simulation method, does not cater to the presence of moving bottlenecks, which may be caused by buses traveling within a network. This may affect the dynamics of congestion that is present and may also affect route choice by all vehicles on a network. The main contribution of this paper is to provide an analytical formulation for a mixed traffic system that includes cars and buses, which realistically replicates moving bottlenecks. We modify the CTM model using methods from the lagged CTM to recognize speed differentials between the free-flow speed of buses and cars. In addition, the impact of capacity reduction caused by buses was incorporated. These developments led to the replication of moving bottlenecks caused by buses within the CTM framework. The formulated variant of CTM was utilized to determine a system optimal assignment that minimizes the total passenger travel time across cars and buses. The proposed modified CTM model, defined as the BUS-CTM, has been applied on a road link and a more detailed network to demonstrate the effectiveness of the approach. The numerical results and the depiction of the bottleneck phenomenon within the model suggests that the BUS-CTM obtains more realistic results compared with the application of the traditional CTM in a mixed car-bus transportation system. The sensitivity analysis shows that bus passenger demand, passenger occupancy of bus, and bus free-flow speeds are the key parameters that influence the system performance.

An experimental study of the Online Information Paradox: Does en-route information improve road network performance?

This study investigates the empirical presence of a theoretical transportation paradox, defined as the “Online Information Paradox” (OIP). The paradox suggests that, for certain road networks, the provision of online information deteriorate travel conditions for all users of that network relative to the situation where no online information is provided to users. The analytical presence of the paradox was derived for a specific network structure by using two equilibrium models, the first being the Expected User Equilibrium (EUE) solution (no information scenario) and the other being the User Equilibrium with Recourse (UER) solution (with information scenario). An incentivised computerised route choice game was designed using the concepts of experimental economics and administered in a controlled laboratory environment to investigate the physical presence of the paradox. Aggregate statistics of path flows and Total System Travel Costs (TSTC) were used to compare the experimental results with the theoretical findings. A total of 12 groups of 12 participants completed the experiment and the OIP and the occurrence of the OIP being significant was observed in 11 of the 12 cases. Though information increased travel costs for users on average, it reduced the volatility of travel costs experienced in the no information scenario indicating that information can achieve a more reliable system. Further replications of similar experiments and more importantly field based identification of the phenomena will force transport professionals to be aware of the emergence of the paradox. In addition, studies such as this emphasise the need for the adoption of adaptive traffic assignment techniques to appropriately model the acquisition of information on a road network.

Systemic Evaluation of the HERO-Based Ramp Metering Algorithm Using Microsimulation: Demonstration Analysis Using a Sydney Motorway

Ramp meters impact not only the performance of the motorway, but also the performance of the arterial road network. The available literature on the HERO ramp metering system is used to implement it as closely as possible using AIMSUN Application Programming Interface (API). The implemented algorithm is evaluated using a network wide approach. In addition, a set of novel measures are introduced that facilitate the evaluation of the impacts of a ramp metering system on the entire network.