During the past thirty years, there has been a steady growth in the size and number of ships
that use the Strait of Istanbul (Bosporus), which is one of the most difficult, crowded, and
potentially dangerous waterways in the world. There have been over two hundred accidents
over the past decade resulting in loss of life and serious damage to the environment. Many
of the proposed export routes for forthcoming production from the Caspian sea region pass
westwards through the Black Sea and the Bosporus en-route to the Mediterranean Sea and
world markets. The risks and dangers associated with tanker navigation, maritime accidents
and environmental catastrophe are aggravated with the increase in the density of traffic,
tanker size and cargo capacity, as well as the nature of the cargo. In order to ease the
problem, a Traffic Separation Scheme (TSS) was established and approved by IMO in 1994.
This scheme has drastically reduced the number of collisions. However, one-way or two-way
suspension of traffic in the Bosporus is inevitable for ships that cannot comply with the TSS
because of their type, size or poor manoeuvring characteristics. The selection of size criteria
to comply with the TSS has been a matter of discussion. This paper presents the results of
a real-time simulation study investigating the manoeuvring performance of large tankers in
the Bosporus. The study was conducted with a simulator capable of subjecting a given hull
form to any combination of environmental conditions, i.e. wind, current and wave drift
forces. The results indicate that, when realistic environmental conditions are taken into
account, the size of ships that can navigate safely in compliance with the traffic separation
lanes is limited.