This study proposed distcriminant models which can recognize dangerous approaching vehicles by using their position and speed which can be measured from road side sensors. It aims to develop road side warning facilities for collision avoidance at small unsignalized junctions. According to the analysis of vehicle behavior approaching to junctions, it is found that 90% of stopping vehicles begin their braking during 30m and 10m from the junction, and the beginning point is influence by the width of street on which they are moving. From results of discriminant analysis between dangerous approaching vehicles and safe approaching vehicles using speed and change of speed variables as explanation indices, it is clarified that around 90% of samples would be distinguished correctly and appropriate sensing areas referring to street's width were found.