PROBLEM TO BE SOLVED: To form an alert-groove on a road surface which notifies a driver or the like of lane deviation by a large sound and vibration by making an attention groove forming device merely advance straight once in one direction.SOLUTION: A front face 21 being a front end and a rear face 22 being a rear end are arranged in a vertical direction, a front inclined face 23 is extended up to the lowest side 231 which forms the lowest part 23a toward an obliquely-downward rear side from a lower side 211 of the front face 21, a rear inclined face 24 extending to an obliquely-upper rear side from the lowest side 231 is joined to the lower side 221 of the rear face 22 at a position which is higher than the lower side 211 of the front face 21 in a vertical direction, and alert groove forming attachments 2 having shapes in which linear distances from the front face 21 of the lowest part 23a are about one fifth with respect to linear distances from the rear face 22 to the front face 21 are detachably attached to an alert-groove forming device 1 at a prescribed interval W in one direction D1 at an interval from one end 121 of a peripheral face of a rear wheel 12 in a width direction, and also at a prescribed interval W in the other direction D2 at an interval from the other end 122 of the peripheral face of the rear wheel 12 in the width direction, thus constituting the alert-groove forming device.SELECTED DRAWING: Figure 1
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