A safety system comprising a vehicle identifier arranged to a moving vehicle or work machine and capable of radio communication and, arranged in an operating connection therewith, an alarm unit, and a personal identifier arranged in connection with the moving unit and capable of radio communication, the personal identifier comprising an alerting device for warning of vehicles or work machines in the area, and said alarm unit comprises warning equipment for warning of moving units in the area, in which safety system, wherein the vehicle identifier and/or the personal identifier is configured to determine a distance between the vehicle identifier and the personal identifier on the basis of at least one radio signal transmitted between the vehicle identifier and the personal identifier; the vehicle identifier is configured to activate the warning equipment if the determined distance between the vehicle identifier and the personal identifier is less than a threshold value determined in advance for the vehicle identifier; and the personal identifier is configured to activate the alerting device if the determined distance between the vehicle identifier and the personal identifier is less than a threshold value determined in advance for the personal identifier; characterized in further comprising a counter radio capable of radio communication, in which safety system the personal identifier is configured to determine a distance between the personal identifier and the counter radio on the basis of the at least one signal transmitted between the personal identifier and the counter radio; and the personal identifier is configured to interrupt the transmission of the at least one signal transmitted between the vehicle identifier and the personal identifier and the activation of the alerting device and warning equipment if the determined distance between the personal identifier and the counter radio is less than the threshold value determined in advance for the counter radio. the vehicle identifier and/or the personal identifier is configured to determine a distance between the vehicle identifier and the personal identifier on the basis of at least one radio signal transmitted between the vehicle identifier and the personal identifier; the vehicle identifier is configured to activate the warning equipment if the determined distance between the vehicle identifier and the personal identifier is less than a threshold value determined in advance for the vehicle identifier; and the personal identifier is configured to activate the alerting device if the determined distance between the vehicle identifier and the personal identifier is less than a threshold value determined in advance for the personal identifier; characterized in further comprising a counter radio capable of radio communication, in which safety system the personal identifier is configured to determine a distance between the personal identifier and the counter radio on the basis of the at least one signal transmitted between the personal identifier and the counter radio; and the personal identifier is configured to interrupt the transmission of the at least one signal transmitted between the vehicle identifier and the personal identifier and the activation of the alerting device and warning equipment if the determined distance between the personal identifier and the counter radio is less than the threshold value determined in advance for the counter radio.