PURPOSE: To enable a moving body such as an automobile to always move at an instructed average speed, by comparing the moving speed of the body with a prescribed reference speed and indicating whether or not the moving speed is conicident with the reference speed.

CONSTITUTION: The number of revolutions of a wheel 1 of a moving body such as an automobile is detected at 3 and changed into pulses corresponding to the movement distance. The pulses are counted by a trip meter 4 to display the movement distance on a distance indicator 5. An average speed is previously set as a reference by an average speed appointer 7. A reference cost time is calculated from the movement distance by a distance-to-time conversion circuit 6. A real cost time measured by a timepiece 8 is compared with the reference cost time. A deviation indicator 10 shows a result of calculation as delay or lead to the instructed time. The moving body is caused to move depending on indications on the indicator 10. As a result, the body can always move at the set average speed.