Fig.4.4 and Fig.4.5 show the results for deviated maximum lateral distance from the original course with function of the S12/L1 for the case of overtaken and overtaking vessel. In this case, the wind effect was not taken into account. The lateral separation between two ships was chosen to be 0.3 to 0.5 times of L1 under the condition of L2/L1 = 1.0. The control gain constants used in these numerical simulation are K1 = K2 = 2.0, K3 = 0.0, K1 = K2 = 5.0, K3 = 0.0

K1 = K2 = 2.0, K3 = -1.0, K1 = K2 = 5.0, K3 = -1.0, respectively and U2/U1 was taken as 1.2 in h/d1 = 1.2. In Fig.4.4 and Fig.4.5, an overtaken vessel's course is not largely deviated from the original direction under the condition of δmax = 10° regardless of the separation between two ships and control gain constants. Also, an overtaking vessel's course is not almost deviated from the original course under the condition of δmax = 5° regardless of the control gain constants, even though lateral separation between two ships is about 0.3 L1 . Furthermore, if the lateral separation between two ships is about 0.5 times of ship length, an overtaking and overtaken vessel is not almost deviated from the original direction under the condition of δmax = 5° regardless of the control gain constants.