During the Arctic Demonstration and Exploratory Voyage (ARCDEV) in April/May 1998 to the Kara Sea extensive continuous electromagnetic (EM) ice thickness measurements were performed along the route on board the icebreaker KAPITAN DRANITSYN. The measurements were compared with ship speed and power data.The ice thickness distribution along the ships track correlates well with the overall convoy speed, regardless of the actual delivered power. There is less correlation when DRANITSYN made her way as a leading ship at constant power. Linear equations are given to predict the convoy speed for a given ice thickness. The variance of these relations can be explained as the result of highly variable ice conditions and properties, in contrast to the homogenous level ice normally chosen for full-scale ice trials. Thus, our data can be taken to principally evaluate the usefulness of along track EM ice thickness measurements for the improvement of ship performance models.