'What would have happened, had I taken the alternative route?' This is a question that many drivers often ponder, hoping that their chosen route is the best. This paper proposes DoppelDriver, a system that attempts to answer such questions on non-chosen alternative routes to a given destination by determining actual times of arrival (ATAs) from participatory users on the non-chosen routes. DoppelDriver offers a direct, actual travel time comparison among route choices. With DoppelDriver's collection of actual travel time comparisons, users will be able to make strategic decisions on, and self-assessments of, their route choices. Also, we describe the potential usage and benefits of ex-post feedback (i.e. travel time on non-chosen routes) and how snapshots of travel time comparisons can be used to support strategic decision making on the choice of a route. Using real taxi GPS data, we investigate whether aggregating ATAs for road segments from other users mimics the ATA for the intended origin-to-destination route. Finally, we present our system design for a prototype implemented on the Android platform.