Shipborne AIS provides independent traffic information to the bridge lookout on duty. This study examines the effect of AIS enhanced bridge lookout operation by means of a ship simulator. The two groups of participants, all qualified British deep sea deck officers, undertook identical simulation scenarios, but one group had the AIS on and the other did not. Significant differences were found between the two groups in reading the targets' privileged status and handling the head-on situation. Those with AIS information were found to avoid possible collisions faster than the group for whom AIS information was not available.