Among other things, a signal is emitted from a signaling device and is captured by stimulus detectors location on a vehicle, including an autonomous vehicle. Properties of the signal are analyzed, potentially in concert with other information, to determine the precise location of the signaling device and therefore the precise goal location for picking up a rider of the autonomous vehicle. In response to the calculation of the precise goal location, the autonomous vehicle attempts to travel to a location as near as possible to the precise goal location to facilitate entry of the rider into the vehicle.