Does the "Mandatory drive straight" sign apply at the nearest intersection or at the point where a change of direction is possible?

In the video you are coming down a slip road towards the main road; at the end of the slip road there is sign A-7 "give way" and below it a blue round sign with a white arrow pointing up - C-5 "go straight on". Sign C-5 applies at the nearest junction or at the place where it is possible to change direction. The answer is: yes.

The Regulation on road signs and signals states that signs ordering the direction of travel, including C-5 "go straight on", require the driver to travel in the direction shown by the arrows and apply at the nearest junction or at the place where it is possible to change direction. This is an important point: the order does not continue along the whole road, it only decides about the nearest place where you could turn - this may be a junction, but also the end of a slip road, an access to a property (zjazd) or the entry to a roundabout. In the video C-5 stands at the end of the slip road, before you enter the main road, and it means that at this point you may only go straight on, without turning left or making a U-turn; beyond this point the sign no longer applies. Sign A-7 above it reminds you that when entering the main road, you give way to everyone travelling on it.

Legal basis: § 35 para. 1 and 2 and § 5 para. 5 of the Regulation on road signs and signals