The National Advanced Driving Simulator (NADS) is a high fidelity simulator developed by the National Highway Traffic Safety Administration (NHTSA) and located at the University of Iowa. The NADS is a tool that allows fundamental research into the complex interaction between driver, vehicle, and roadway. To facilitate that goal, the NADS has been designed as a shared-use facility whose operating model allows researchers from laboratories, academia, and industry to design and test simulation scenarios on consumer class personal computers before using them on the NADS. A set of software components were designed and implemented to allow this off-line specification of scenarios. These software components are cumulatively referred to as Scenario Definition and Control (SDC). This paper overviews the NADS SDC software and how it can be used for developing driving simulation scenarios through the use of the Interactive Scenario Authoring Tool (ISAT).