An investigation into the way in which human operators control a ship model on a straight course is described and the results presented and discussed. Some experiments were carried out in a simulated cross-wind and a comparison is made between calculated equilibrium drift and rudder angles and those actually used by the operators. Various parameters relating to controllability (with special reference to controllability in port approach channels) are presented, and overall values for navigation lane widths both with and without cross-winds are deduced.