PURPOSE: To prevent bumping accident by providing a sensor to an opening and closing bar to open in response to the operation of a handle for issuing a warning to driver.

CONSTITUTION: An opening and closing bar 2 is supported by an elastic plate 20 which opens at a pin bar 15 as a shaft in response to the operation of the handle by a wire 6. And, the bar 2 is opened according to inner ring difference in response to the operation of the handle. Also, the bar 2 is provided with contacts 9 and 10 which issue a warning to the driver when contacting with human body, etc. Since the bar 2 can open according to the operation of the handle, human body, etc., present within inner ring difference can be sensored and therefore, bumping accident can be prevented.