A control program for a combination vehicle including a tractor and a trailer that is towed by the tractor, the control program being a program that causes a computer to perform a state quantity acquisition process, a predicted trajectory information calculation process, and a display process, wherein:
- the state quantity acquisition process is a process of acquiring a state quantity of the combination vehicle;
- the predicted trajectory information calculation process is a process of calculating predicted trajectory information of the trailer according to the state quantity;
- and
- the display process is a process of displaying the predicted trajectory information by operating a display device.