Recently, welfare vehicles are widely used among the elderly and the aged. However, it is not easy for inexperienced beginners or the aged to control the welfare vehicle in narrow places such as corridors. In this paper, a driving assistance system using Mixed Reality (MR) which has collision avoidance function is proposed using a virtual platoon control scheme. Using the system, it is supposed that the cognitive and driving ability is enhanced from the simulated objective view point. The driver rides on the vehicle and controls using the virtual preceding vehicle on a Head Mounted Display (HMD). The virtual vehicle projected on a HMD is steered from a simulating objective viewpoint, and the welfare vehicle is controlled so as to follow the virtual vehicle using the precise platoon control algorithm. In order to avoid the collision to obstacles by the beginners, the obstacle avoidance function on the assistance system is designed using MR technology. To detect obstacles or the wall, the proposed assistance system uses 3D mapping function of a HMD. As a result, it is confirmed that collision can be avoided safely by driving experiments in the narrow corridor.