The positioning service of Quasi-Zenith Navigation Satellite System (QZSS“Michibiki”) has launched on November, 2018 in Japan involved by Cabinet Office, Government of Japan  . This study focused on a development of support system for snowplow operation which is combined with the real time positioning information acquired from GNSS including QZSS and the three dimensional road facility information acquired from mobile mapping system (MMS) equipped with digital photograph and laser devices. The system has been consisted of four components which are moving window displaying, recognition of road facility, guidance and alarm at real time processing for the snowplow operation corresponding to a vehicle speed. In addition, this study attempted a validation for the performance of the system in the test site of an expressway in the northern part of Japan. The precision of mapping of road facilities by means of MMS was less than 0.027 m in horizontal direction and less than 0.045 m in vertical direction, then point cloud data set was reconstructed into vector typed data set with attribute data for three dimensional landscape features including highway road facilities  . The vector type data was real-timely processed with QZSS down linked signals on a vehicle using a receiving device, AQLOC-VCX equipped with INS  . The validation on the official precision which are less than 12 cm of horizontal direction and less than 24 cm of vertical direction was performed by means of centimeter level augmentation service (CLAS) of QZSS which provide the corrected positioning information based on the existing continuously operating reference stations of GNSS provided from GSI in Japan  .