FIG. 17A illustrates a screen of prior notice displayed at the monitor device 24 corresponding to the front windshield 15 in FIG. 16A. As illustrated in FIG. 17A, in addition to the symbol image 37′ indicating the scheduled travel course, a symbol mark 53′ formed as an arrow mark indicating a travel course for lane change is displayed at the behavior display area 35a of the monitor device 24 having the scenery 39 taken by the front camera as a background. Here, the symbol image 53′ may be displayed instead of the symbol image 37′.