An apparatus and a method are disclosed for tracking a plurality of targets (e.g. land-based vehicles). The method can include: for a first time-step, estimating a state of each respective target; at a second time-step, measuring values for a state of each target; for the second time-step, estimating a state of each target using the estimated target states for the first time-step; updating the estimated target states for the second time-step by performing a Joint Probabilistic Data Association process using the measured values; and performing an identity management process to estimate a probability that a particular state measurement corresponds to a particular.