Serious games became an important device for increasing the awareness of issues that are important to society. One such issue is the environmental impact of driving. To support the training and wide promotion of eco-friendly driving, an appropriate platform and tools are needed. In this paper, we present the Scenario Markup Language (SML), a simple yet expressive language for authoring realistic traffic situations. This effort is part of a novel framework for automatically generating complex scenarios in the transport domain. In particular, SML facilitates the scripting of behavioral driver studies in multi-user online three-dimensional (3D) virtual worl