After many years of data scarcity in transportation-related sciences, we have now entered the era of big data. Large amounts of data are available from GPS devices, mobile phone traces, payment transactions, social media, and other sources. The opportunities that this new availability presents are enormous. High-quality data is available at very low or negligible cost. These data can be used to develop new tools, to explore and understand travel behavior and to formulate new policies. However, the challenges are also big: the access to the data is not guaranteed, confidentiality has to be considered, the capacity of processing and enriching these databases has to be developed, and only then will they become really useful for decision-making and for the definition of public policies. This chapter presents an overview of the current state of play, and discusses the future perspectives, focusing on the challenges of building new predictive models.