PURPOSE: To prevent a traffic jam in the construction section by detecting the traffic amount by a sensor and automatically adjusting the passage time and waiting time of the halfway of up and down lanes according to the traffic amount.

CONSTITUTION: Sensors 1 and 2 counting the number of cars of the up and down lanes are provided on the shoulder outside an intersection line (a) on the road of the up and down lanes outside the construction section A. A controller 3 uses the sensors 1 and 2 to repeatedly measure the traffic amount of the up and down lanes in the temporary setting time. Based on the measurement result, the maximum value of the passage time (a green light period) of the traffic signal 4, 5 for construction is decided. The controller 3 controls the maximum value to correct the maximum value based on the information from the sensors 1 and 2 to be measured. In short, the passage time and waiting time of the up and down lanes of the construction section A of the halfway passage can be automatically adjusted.