Do you have to signal when there are no cars around?

It depends on the specific laws in your jurisdiction but generally, the answer is no. In most places, you are only required to signal when you are changing lanes or turning, and only when there are other vehicles around that could be affected by your maneuver. However, there are some situations where you may want to signal even if there are no cars around, such as when you are entering or leaving a roundabout. Ultimately, it is best to check the local traffic laws to be sure.