The decision support system RODOS (Ehrhardt and Weis, 2000) contains a large set of simulation models, data bases, user interfaces and system functionalities. However these many options resulted in heavy-weight and complex user interfaces difficult to handle by non-experts. For this reason a user friendly and light-weight access to the RODOS functionalities was requested by the end users. This was fulfilled by the design and implementation of a new user interface named RODOS-Lite. The main purpose of this redesigned user interface is to gently lead operators through a sequential line of input masks, hiding rarely used parameters (defaults are set) from the operator but still providing the possibility to access them if necessary. Additionally, the interface is strongly safeguarded to prevent operators from entering wrong input values. This is achieved by systematically checking input values and even suggesting occasionally best estimate parameters. RODOS-Lite is complemented by various simple but nevertheless extremely useful features such as online access to Google maps or source term visualisation.