When driving behind a vehicle that is travelling at a speed of 80 km/h on a road marked in this manner, is it mandatory to keep a minimum distance of at least 40 meters from it?

In the picture, the blue sign with a symbol of two roadways and a flyover is D-9 "motorway". When driving on a road marked in this way behind a vehicle at a speed of 80 km/h, you must keep a distance of at least 40 m from it. The answer is: yes.

The Regulation on road signs and signals states that sign D-9 marks the beginning or continuation of a motorway. The Road Traffic Act requires a driver travelling on a motorway or an expressway to keep a minimum distance from the vehicle in front of them in the same lane, which in metres must be no less than half the number showing the vehicle's speed in km/h; this rule does not apply when overtaking. The calculation is simple: 80 km/h divided by two gives 40 m - this is the statutory minimum, and the law provides for a fine and penalty points for breaking it. The distance is measured to the vehicle in the same lane, so it applies precisely to driving "behind" someone. Forty metres at 80 km/h is just under two seconds of driving - as much as you need to react and start braking; at higher speeds or on a worse surface, you increase the distance. Buses and vehicle combinations with a trailer travelling at 80 km/h on a motorway follow the same rule.

Legal basis: Art. 19 para. 3a of the Road Traffic Act (Prawo o ruchu drogowym); § 48 para. 2 of the Regulation on road signs and signals