What is the minimum safe following distance (sigurnosno odstojanje) that a heavy commercial truck driver should maintain behind a leading vehicle at 80 km/h on an open road in dry weather?

1. A distance corresponding to at least 4 to 5 seconds of travel time (approx. 90 to 110 metres)
2. A distance of exactly 5 metres
3. A distance corresponding to 1 second of travel time
4. One truck bumper length