Distance warning device and method for improving road safety

The method involves measuring rear spacing (4) between front vehicle (1) and subsequent vehicle (2). The measured distance is compared with predetermined safety distance, and stored in data memory (9) of front vehicle. An optical signal (7) is displayed in front vehicle and warning message is transmitted to subsequent vehicle when measured distance is below the predetermined safety distance, after confirmation of the driver of front vehicle. Independent claims are included for the following: (1) a spacing warning device of front vehicle; and (2) a vehicle.