Marine traffic engineering has been pushed to the limits due to a rising demand in the shipping business. Merchant ships are growing dramatically, both in numbers and in size. To keep pace with current developments, automation seems to be one viable option when it comes to keeping ships running with fewer seafarers available. The aim of this paper is to monitor a modern day mariners’ performance while working in a tense situation. The objective is to define the size of the safety domain whilst overtaking a vessel. The approach was to assess the ship’s domain area within a 3 nm wide traffic separation scheme by using a ship handling simulator. From the simulation results, an overtaking domain was determined as 1.36nm long and 0.4nm wide. Safety domains in real-life situations were experienced on a much smaller scale compared to the previous findings. The working load for this particular operation is expected to be stressful and highly skilled orientated.