The rotary snow blower vehicle operated for removing accumulated snow on road shoulders must be performed even in conditions of a poor visibility due to a snowstorm or road markings completely covered by snow. The operators of the vehicle must pay full attention to avoid contacting road structures and ordinary cars passing just beside the snow blower. Therefore, we have developed a high-precision snow blower positioning device using a quasi- zenith satellite system and a high-precision expressway map for the first time on the expressway in Hokkaido, Japan. The device can precisely indicate the exact position of the snow blower on expressways in real time and the operator can drive the vehicle by watching a monitor showing the assistant information provided by device.