1. A trajectory data retrieval system ( 1 ) for retrieving trajectory data of moving objects in a plurality of image sequences, the trajectory data retrieval system ( 1 ) comprising: a processor having a database ( 4 ) configured to store and index a set of common routes based on the trajectories of the moving objects, whereby each subset of the set of common routes is generated by a plurality of trajectories and whereby each subset is linked with the trajectory data of generating trajectories of said each subset, or parts thereof or of trajectories overlapping at least in part with the subset, querying means ( 7 ) configured to formulate a trajectory-based query, the querying means ( 7 ) comprising translating means for translating trajectory-based queries in terms of common routes, common nodes (A, B, C, D, E, F, G, H) or both, and retrieval means ( 8 ) configured to retrieve trajectory data linked to a matching subset of the set of common routes matching with the trajectory-based query, wherein the querying means ( 7 ) comprises means for formulating an area-of interest query, a line-crossing query or a trajectory-by-sketch query, a trajectory-by-example query, a one-click-trajectory query, or any combination thereof.