5. Traffic Simulation with Aimsun

This chapter is dedicated to the Aimsun transport simulation software, with particular emphasis on its dynamic simulation capabilities. The main topics discussed are the modelling of section dynamics using microscopic and mesoscopic approaches, and algorithms for solving the dynamic traffic assignment problem. The introductory section provides background information together with a discussion of the development principles behind Aimsun: integration, modularity, scalability, interoperability, and extensibility. Section 5.1 provides an overview of the project development process covering model building, verification, calibration and validation, and analysis of outputs. Section 5.3 outlines the logic of the microscopic and mesoscopic simulation processes along with information about the behavioural models at each level. Solving the dynamic traffic assignment problem using Aimsun is the focus of Section 5.4. We cover three different methods for tackling the problem, based on dynamic user equilibrium (DUE) and stochastic route choice models with and without memory. In Section 5.5 we turn to the subject of calibration and validation of Aimsun models. This section describes different Aimsun tools which can be used for verification and validation, and provides guidelines or examples relating to the calibration of behavioural models and dynamic traffic assignment algorithms. Section 5.6 looks at the methods that can be used to extend Aimsun’s modelling capabilities. It covers both working with external applications and the use of various programming tools. Α selection of advanced case studies and applications is the focus of Section 5.7. It describes how Aimsun has been used to solve transportation engineering problems with reference to three real-world examples.In the final section, we describe Aimsun Online and discuss its implementation in Madrid as an advanced case study. In the latter part of the section, we comment on some challenges related to such applications and the development needs that such projects give rise to.