If that is your private driveway then that is rather odd, I mean
is that actually pretty clear that it is a private driveway ?
Only thing I can think of is go up to them and tell them they are trespassing, or if they leave before you reach them get their license plate, or at the very least make and color of car and call the police.
To be honest I think it's harmless, I mean no serious criminal intent on breaking in would advertise their intent that blatantly in advance would they when they could just as easily have done it on foot where you would never have been any the wiser.
Maybe an ex-lover who couldn't take no for an answer.