A route planning system comprises a receiver component that receives a request for directions between a beginning point and a destination point. An analysis component analyzes a traffic system representation that varies as context varies and outputs expected amounts of travel time between the beginning point and the destination point for multiple contexts based at least in part upon the analysis. A method is described herein that includes techniques for searching over routes and trip start times simultaneously so as to identity start times and routes associated with maximal expected value, or equivalently minimum expected cost, given preferences encoded about one or more of the leaving time, the travel time, and the arrival time.