The Smart Trek Model Deployment Initiative, a US Department of Transportation-funded intelligent transportation systems program in the Puget Sound region, has made great strides in integrating and disseminating traveler information. The initiative focuses on real time information to help travelers make informed decisions about their travel options. The Smart Trek project has brought about a variety of real time transit information applications. One of these is MyBus, which makes departure predictions and delivers traveler information to Web browsers and cell phones. MyBus aims to present to riders, in real time, the predicted departure times of buses at specific locations throughout a transit region. King County Metro, Seattle's transit agency, operates a large fleet. Up to 1200 vehicles are in service simultaneously, departing from over 1000 locations. MyBus predicts approximately 210000 weekday and 140000 weekend scheduled departure events. This is over a million departure predictions per week. MyBus has shown that predictions on this scale are feasible and manageable. Several technologies are central to the success of MyBus. A common format for the transit agency schedule and spatial data was crucial, letting us redeploy the Seattle pilot project with data from the Portland Tri-Met transit agency with minimal effort. The format we chose was a database schema based directly on the Transit Communications Interface Profiles standards.