PURPOSE: To contribute of traffic safety enabling the digitally displayed running speed of a car to read on the outside of a car.

CONSTITUTION: A speed displaying device 3 is provided for instance under the front bumper 2 of a car 1. This device 3 is constituted so that a speed display part 3a prepared in front of the device may display digitally the running speed of the car 1 in the order of km/hr and at three figures. Thus, the running speed of the car 1 can be read easily on the outside of the car 1. Therefore drivers of cars which run facing each other in their neighborhood can certify the speeds of their opposite cars, keep proper distance between cars and find violators of the speed limit rule easily.