Virtual simulations are an effective instructional methodology for preparing responders to function in the field: so much so that a large percentage of State Fire Directors are in the process of adopting computer simulation as the basis for incident command training. First-hand efforts to provide pre-made simulation scenarios to instructors have resulted in strong demand and encouragement, accessed consistently many thousands of times per month. In spite of today's Internet-connected world, however, simulation creation remains an expensive, time- consuming, isolated, and offline endeavor due to limitations of the available development tools. The proposed project, uSim, is a game-changer. Imagine a web site that permits instructors collaboratively to create a scenario, or select an existing scenario and change the pictures and hazards to reflect local conditions, or extend in new ways. Furthermore, the simulations can be accessed and shared as easily as sharing a YouTube video. The platform will enable instructors to exploit the benefits of simulation in the live and virtual classroom while dramatically reducing development time through collaboration. The proposed approach takes advantage of the team's substantial expertise with simulation tool development and subject- matter experience, having pioneered and operated a market-leading, award-winning platform for safety training. The Phase I research aims are to: (1) develop a web-based repository and integrated builder application for creating and viewing virtual simulations;(2) enable member instructors to adapt, localize, and extend existing simulations via a permission-based authoring mechanism that supports collaborative scenario development;and (3) create example Fire Service and HazMat scenarios. Initial commercialization will follow Phase I through the team's existing traction in the Fire Service market, with Phase II research extending collaborative and deployment features, as well as content development throughout other safety training domains. The application is rated at a priority score level of 28.