A sliding door is one of the car door systems, which is generally applied to the van-type vehicles. Compared with typical swing door systems, a sliding door gives a comfort to the passengers when they get in or out the car. With an increasing number of the family-scale activities, there followed a huge demand on the van-type cars, which caused growing interests in the convenience technology of the sliding door system. A typical sliding door system has negative effects on the vehicle interior package and the manual operating effort. Since the door should move backward without touching the side outer panel, the trajectory of the center rail should be a curve. The curve-shaped center rail infiltrates not only the passenger shoulder room, but also the opening flange curve, which results in the interior package loss. Moreover, as the passenger pulls the door outside handle along the normal direction of the door outer skin, the curve-shaped center rail causes a loss of the manual operating effort. In this study, we will discuss not only how the curve-shaped center rail causes negative effects on the vehicle interior package and the manual operating effort, but also how to effectively improve and optimize the sliding door system. Moreover, we will propose a new design concept of a convenient sliding door center rail and roller. By applying a straight center rail and a latch with a multi-link structure, we were able to decrease the center rail infiltration about 120mm compared with the typical sliding door system. Also, the performance of getting on and off the 3rd row was improved, and the manual operating effort was improved about 60%.