Abstract
Today's one-size-fits-all approach to travel-time computation in spatial networks proceeds in two steps. In a preparatory off-line step, a set of distributions, e.g., one per hour of the day, is computed for each network segment. Then, when a path and a departure time are provided, a distribution for the path is computed on-line from pertinent pre-computed distributions. Motivated by the availability of massive trajectory data from vehicles, we propose a completely on-line approach, where distributions are computed from trajectories on-the-fly, i.e., when a query arrives. This new approach makes it possible to use arbitrary sets of underlying trajectories for a query. Specifically, we study the potential for accuracy improvements over the one-size-fits-all approach that can be obtained using the on-the-fly approach and report findings from an empirical study that suggest that the on-the-fly approach is able to improve accuracy significantly and has the potential to replace the current one-size-fits-all approach.