Reviewing previous studies on using computational models for analyzing the effect of transport policies on transportation systems shows that agentbased models have not been used much in spite of their great potential for simulating dynamic aspects of policy instruments and travel behavior. The main reason can be the need for a lot of input data which is hard to prepare for the modeler. This has led to limited use of agent-based models in previous studies and even in those studies the scope of simulation is limited to only particular scenarios. In this thesis, I proposed a general-purpose agent-based simulation model for urban transportation that supports simulation of a wide range of policy instruments. The proposed model is designed in a way that a large part of the input data can be generated automatically using online web-services. The thesis also reports an empirical study on using our proposed generalpurpose model together with on-line travel planners in agent-based simulation for predicting the effect of different policy instruments on travel behavior. The results from our empirical study showed that our generalpurpose agent-based model predicts 72% of the real travel decisions correctly. Furthermore, the results of the simulation for various scenarios and combination of them seem to be acceptable. Finally, we found out that the use of on-line services for data collection increases the speed and flexibility of the system for defining and running new scenarios. However, the scalability of using on-line services in simulation is constrained by limitations of online service providers. The main contributions of this thesis are a general-purpose agentbased simulation model for urban transportation and a novel approach to automatically generate input data to the simulation using online travel planners and other web-services. This novel approach mitigates the challenge of agent-based simulation as a data-intensive method. This can lead to more widespread use for agent-based simulation in solving complex and realistic transportation scenarios. Another contribution of this thesis is on visualization of simulation output. One of the main challenges of using simulation systems by transport planners and decision makers as end-users is to understand the complex output of the simulation. In this thesis, I empirically demonstrated how the usability of a freight transport simulation system is improved by adding a visualization module that illustrates the results of the simulation for the end-users.