Background Urban travel demand forecasting models are an essential planning tool in planning and policy development. These models range in level of detail and comprehensiveness, depending on various factors including the availability of good quality data on travel and traffic in the area of interest. Household travel surveys form the major source of information on local travel patterns and trip making characteristics, and provide inputs into model development. While these surveys provide a rich database on households, persons and trips made by them, they are seldom complete. There is a large array of travel segments that are not typically captured by these surveys, for example, trips made by persons who live in group quarters (e.g., campus residences) and trips made by non-residents visiting or travelling through the region. In addition, there are a number of trips made by various vehicle types that are not adequately addressed in urban travel models, such as emergency response, garbage collection, and private transit vehicles, etc. Study Details The purpose of this research is to explore various travel and traffic segments, with a view to identifying how they are accounted for in modeling and planning applications, using the Greater Toronto and Hamilton Area (GTHA) as a case study. Two main data sources in the GTA, i.e., the Transportation Tomorrow Survey (TTS) and Cordon Count Data are analyzed, within the context of travel demand models in use in the GTA, to provide insights. The main finding from research will be to develop an understanding of the size of these segments of travel that are traditionally unaccounted in urban models. This knowledge will be useful when applying demand forecasts from such models to aid planning, policy development and evaluations.