| The planning, management, and operation of transportation systems requires sophisticated modeling tools that closely reflect reality (Ortuzar and Willumsen, 1994), so that the cost and benefits of different scenarios and options can be effectively and efficiently evaluated. In the past decade, new approaches have been developed to augment and improve the components of existing platforms and to seek new modeling paradigms. It is timely to take stock of what has been developed so far and to provide a preview of what lies ahead. This special issue is a collection of advanced papers that were presented at the International Conference on the Application of Information and Communication Technology in Transport Systems in Developing Countries, which was held in Sri Lanka from 5 to 7 August 2004. These papers cover some of the most recent modeling advances in the planning, management, and operation of transportation systems.
The emerging modeling issues for the planning of transportation systems include land use and transportation interaction (Haghani et al., 2003; Lee et al., 2003), network reliability (Lam, 1999; Bell and Cassir, 2000), network design problems (Magnanti and Wong, 1984; Yang and Bell, 1998; Szeto and Lo, 2005), and sustainable transportation problems (Bernstein, 2001; Black et al., 2002). In the first paper of this special issue, Chootinan et al. present a reliability-based network design problem in which a new capacity-reliability index is introduced to measure the probability of network failure. A continuous network design problem is formulated as a bi-level program, and is solved by means of a genetic algorithm.
The most recent modeling issues to surface in the management of transportation systems include road pricing (Hau, 2005a, b), traffic control (Wong and Lo, 2004; Wong et al., 2005), and the provision of information (Rathbone, 1997; Cashin et al., 2002; Jou et al., 2004). The next two papers in this issue focus on the provision of information for the management of transit and highway networks. Lo et al. develop a passenger route guidance system for a multi-modal transit network that incorporates the state augmented multi-modal model and an automatic speech recognition system. The implementation platform is a web-based geographical information system. Lam et al. establish a short-term travel time forecasting method for the prediction of travel time on the highway network of Hong Kong using a bi-level programming approach.
Current issues in the operation of transportation systems include vehicle dispatch problems (Fu, 2002; Toth and Vigo, 2002; Cordeau et al., 2002; Cordeau and Laporte, 2003; Khattak and Yim, 2004), transit scheduling problems (Eberlein et al., 2001; Poon et al., 2003; Bandara and Ekanayake, 2003; Sun and Hickman, 2004), the development of traffic flow models (Kerner and Konhauser, 1993, 1994; Zhang, 1998; Helbing, 2001; Wong and Wong, 2002; Daganzo, 2002a, b), and the education and training of road users (Kontogiannis et al., 2002; Hatakka et al., 2002; Sullman et al., 2002; Lan and Kuo, 2003; Wong et al., 2004). Although advanced traffic flow models have recently been developed, little research has been undertaken on the problem of mixed traffic streams with a high proportion of two-wheeled vehicles, which is a common problem in developing countries. The penultimate paper of this issue makes a good attempt to address this important issue. Lan and Chang develop a traffic flow model for a mixed traffic stream with motorcycles and cars that uses the cellular automata approach, and provide a modeling platform for the assessment of the impact of motorcycles in a mixed traffic mode. The last paper deals with education and training. Watanabe et al. develop a driver support system, ASSIST, which warns drivers when the headway between their vehicle and the vehicle in front is shorter than the estimated stopping distance. Encouraging results have been obtained from a series of experiments.
The papers that are presented in this special issue are by no means intended to be exhaustive. However, they do provide a general coverage of the important areas of research into transportation modeling. The editors hope that this issue will bring state-of-the-art modeling tools to the attention of practicing engineers and researchers, and will inspire and stimulate new research and efforts in the field to improve the planning, management, and operation of transportation systems.
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