Is it required to maintain a minimum distance of at least 100 metres from the vehicle in front on a road marked in this manner?

Why?

Sign D-7, “Expressway”, does not require a fixed following distance of 100 m. The minimum gap in metres to the vehicle ahead in the same lane must be half your speed in km/h, so at 100 km/h you need at least 50 m. This numerical rule does not apply while overtaking, but you must always maintain a safe distance.

art. 19 ust. 2 pkt 3 i ust. 3a Prawa o ruchu drogowym