Existing literature suggests that mixed land-use developments have the potential to reduce traffic by “capturing” some trips internally and providing a pedestrian-friendly environment to facilitate walking for some trips. However, these elements which are meant to provide the traffic-reducing benefits also reduce the overall cost of travel, thereby increasing the total amount of travel. This “induced” travel has implications for the site planning process, which assumes that all internal trips are replacing trips on the external street network. In this investigation, travel survey data were analyzed to determine the nature and extent of induced travel at mixed-use developments. The study site was a 75-acre suburban infill mixed-use development in Plano, Texas. Features of the study site included a diverse land-use mix, a grid-style street layout, and pedestrian-oriented streetscapes. The travel survey was administered as an interview of persons exiting buildings at the site and gathered information about two trips made by the respondent, including whether the trip made at the time of the interview was induced. A trip was considered induced if the respondent would not have made the trip if it had required travel outside of Legacy Town Center. Analysis found that in the morning, four percent of all trips at the study site were induced; in the afternoon, about one-quarter of all trips were induced. Induced trips accounted for one-eighth of internal trips in the morning and forty percent of internal trips in the afternoon. Most internal trips made in an automobile were replacements for off-site travel while most trips made on foot were induced. Based on this study, it is evident that some internal trips at mixeduse developments are not “captured” from external streets, but represent additional trips, induced by travel cost savings in the mixed-use environment. However, it is demonstrated that, even with this additional travel, mixed-use developments still contribute to a reduction in overall vehicle-miles of travel. Stakeholders are encouraged to consider these findings when evaluating new land-use policies or the traffic impacts of proposed mixed-use developments.

The National Transportation System (NTS) is undoubtedly a complex system-of-systems---a collection of diverse 'things' that evolve over time, organized at multiple levels, to achieve a range of possibly conflicting objectives, and never quite behaving as planned. The purpose of this research is to develop a virtual transportation architecture for the ultimate goal of formulating an integrated decision-making framework. The foundational endeavor begins with creating an abstraction of the NTS with the belief that a holistic frame of reference is required to properly study such a multi-disciplinary, trans-domain system. The culmination of the effort produces the Transportation Architecture Field (TAF) as a mental model of the NTS, in which the relationships between four basic entity groups are identified and articulated. This entity-centric abstraction framework underpins the construction of a virtual NTS couched in the form of an agent-based model. The transportation consumers and the service providers are identified as adaptive agents that apply a set of preprogrammed behavioral rules to achieve their respective goals. The transportation infrastructure and multitude of exogenous entities (disruptors and drivers) in the whole system can also be represented without resorting to an extremely complicated structure. The outcome is a flexible, scalable, computational model that allows for examination of numerous scenarios which involve the cascade of interrelated effects of aviation technology, infrastructure, and socioeconomic changes throughout the entire system.