br Conclusions Despite there has

Conclusions Despite there has been an increased amount of research on “sustainable transportation”, most individual authors, entities, and agencies still do not have an agreed-upon definition of “sustainable transportation”. This poses challenges to the review of existing literature and to the promotion of “sustainable transportation.” An inconsistent definition more or less means that we have a moving target in the collective effort towards “sustainable transportation.” However, this NSC 687852 shortfall seems not to deter individuals, entities, and governmental agencies from engaging in the cause of “sustainable transportation”, as reflected in Tables 1 and 2. Adopting a broadly defined sustainable transportation concept based on synthesizing of selected definitions and classifying existing sustainable efforts with a prescribed taxonomy, this paper finds that sustainable transportation has garnered increased attention at all three levels: research, policy proposal, and program/implementation. However, there are still notable variances, and some of which are gaps to be filled as we muddle through the cause of sustainable transportation. This paper shows that there are significantly more Levels 1 and 2 proposals than Level 3 programs or actions. On the one hand, this reflects the fact that there is always a long way to go before most Levels 1 and 2 proposals are translated into Level 3 ones. On the other hand, there could be possibilities that: The above possibilities open great room for further research, which could help bridge the gaps in and between different levels of research, proposals and/or actions. Some possible research questions for the future are: Particularly, this paper finds that there are notable variances between the sustainable transportation efforts in the US, the UK, and Canada at the national level in the following aspects: Compared to its UK and Canadian counterparts, the US federal government does not have an official definition of “sustainability”, does not have a mandate for departmental strategies/initiatives on sustainable development, and does not have a gateway website for marketing sustainability. But some entities and federal departments in the US have been quite active in pursuing sustainability and sustainable transportation. They even funded at least two in-depth studies of sustainable transportation practices in West Europe. A Canadian researcher was also involved in the development of sustainable transportation indicators sponsored by TRB. At the state and local levels, there have been many efforts to link sustainability to transportation planning processes. The above disconnect between the local/state and federal governments, nevertheless, begets the following research questions that the author can further work on:
Introduction: modeling and simulation in urban studies Computer models in urban studies have their roots dating back to the 1960s (Lowry, 1965) after the scientific concept of Urban System had been coined by emulating terminologies in the field of botany (Duncan et al., 1960). The simulation models, in attempting to provide both descriptive and predictive understandings of the real world by characterizing quantity and relationship in a silicon surrogate of the real world, have found their increasingly wide applications in scientific research with advances in computer power. How simulation has transformed our understanding and how it has revolutionized the world of science have been extensively discussed and publicized in Casti (1997). In particular, Simpson (2001) has provided a comprehensive literature review of the application of virtual reality and simulation models in urban studies. As ambitiously as he has put it: “The combination of virtual reality, spatial modeling, and GIS, integrated into a real-time urban simulation, will allow questions to be asked that were not possible before, and better yet, answers to those questions.” This is exactly what we are witnessing today (see, for example, Dr. Andrew Hudson-Smith\'s constantly updated blog [http://www.digitalurban.blogspot.com/] for a skim of today\'s cutting edge technologies and applications).