Following vehicle detection and alarm device

A following vehicle detection and alarm method, the method comprising:

• imaging an area behind a vehicle of interest with a camera at a predetermined frame rate;
• counting the number of frames after another vehicle is shot in a shooting range of the camera until the another vehicle reaches a first predetermined position behind the vehicle of interest;
• outputting an alarm instruction at a first time that varies based on the counted number of frames, for notifying the driver of the vehicle of interest that the another vehicle is approaching;
• and,
• performing a predetermined alarm operation for the driver when the alarm instruction is output, wherein the predetermined alarm operation is performed at a second time after the alarm instruction is output;
• and,
• wherein the first time is set such that the predetermined alarm operation is performed when the another vehicle passes a second predetermined position closer to the vehicle of interest than the first predetermined position.