In the last decades, the increasing number of vehicles is producing important congestion problems in urban and inter-urban areas. Traffic congestion has many negative effects, such as, wasting time in non-productive activities, delays, pollution, and health problems, among others. For these reasons, the interest in traffic modelling has increased considerably within the scientific community, with the need to develop efficient and easy-to-use models, able to reproduce reality and future traffic situations. This book makes several contributions to transport demand modelling, developing different mathematical models to better reproduce existing traffic conditions. Among them, pointing out methods based on plate scanning for solving the trip matrix and path flows estimation and, tools to deal with the problem of observability of traffic networks. The book contents should be useful to professionals in the sector, or anyone else who may be interested in starting to research in the transport field due to the broad literature review. Its application could also help public administration to elaborate good mobility programs.