Google already showed the self-driving car can do stopping and accelerating more smoothly than the human drivers by doing extensive experiments. In this paper, we compare a human driver with computer generated motion for expressway lane changing. We did experiments at Nagoya ring route expressway and recorded all the detail motion information regarding lateral and longitudinal movement of a taxi driver. We developed an algorithm to generate and evaluate the alternative lane change motion sets considering both lateral and longitudinal trajectories. We defined a smoothness measure that integrates lateral and longitudinal motions to evaluate generated lane change motions. Evaluation results for 19 sets of lane change labeled data show the computer motion generator is able to generate close or better motion compared with a taxi driver using proposed evaluation function.