Tzu-Chang Lee

New Approach to Modeling Mixed Traffic Containing Motorcycles in Urban Areas

Motorcycles constitute a significant proportion of traffic in many countries but are poorly represented in existing traffic flow theories and simulation software. A new approach to modeling mixed traffic is introduced focusing on depicting the movements of motorcycles. In this study, the characteristic patterns of motorcycle behavior were identified, and the key elements contributing to these patterns were extracted. Then three mathematical models were developed to depict these key elements, which were calibrated by using field data collected at Victoria Embankment in central London. After the calibration procedures, these models were integrated into an agent-based simulation model system. The ability of the simulator to reproduce plausible patterns of car and motorcycle behavior was verified. A number of potential applications of this simulator for the management of mixed traffic streams in urban areas are discussed.

Trajectory Data and Flow Characteristics of Mixed Traffic

Models of driving behavior (e.g., car following and lane changing) describe the longitudinal and lateral movements of vehicles in the traffic stream. Calibration and validation of these models require detailed vehicle trajectory data. Trajectory data about traffic in cities in the developing world are not publicly available. These cities are characterized by a heterogeneous mix of vehicle types and by a lack of lane discipline. This paper reports on an effort to create a data set of vehicle trajectory data in mixed traffic and on the first results of analysis of these data. The data were collected through video photography in an urban midblock road section in Chennai, India. The trajectory data were extracted from the video sequences with specialized software, and the locally weighted regression method was used to process the data to reduce measurement errors and obtain continuous position, speed, and acceleration functions. The collected data were freely available at http://toledo.net.technion.ac.il/downloads. The traffic flow characteristics of these trajectories, such as speed, acceleration and deceleration, and longitudinal spacing, were investigated. The results show statistically significant differences between the various vehicle types in travel speeds, accelerations, distance keeping, and selection of lateral positions on the roadway. The results further indicate that vehicles, particularly motorcycles, move substantially in the lateral direction and that in a substantial fraction of the observations, drivers are not strictly following their leaders. The results suggest directions for development of a driving behavior model for mixed traffic streams.

Determinants of powered two-wheelers virtual lane width in urban arterials

The present paper aims at modeling the dynamic width of the virtual lane of the Powered Two-Wheelers (PTWs) and revealing the critical factors that may influence it, such as the speed of the motorcycles, the existence of a heavy vehicle and so on. All possible manners of PTW maneuvering in an urban arterial (2 lanes per direction of travel) were identified and then data were collected from real measurements using advanced video analysis techniques. Further, statistical models were developed in order to reveal the relation between the virtual lanes width and several determinants such as PTW speeds, lane headways, traffic mix and so on. Results showed that the virtual lane width depended on the speed of the PTW, the existence of a platoon, the existence of a heavy vehicle and the headways in both lanes. Moreover, results revealed the need to address the human behavior and the cognitive aspects of driving during the modeling.