The unified texture is efficient, but it is not 4K. If you zoom in with a free camera (Ctrl+F12), you will notice the asphalt lacks the fine grain detail of high-end payware maps like "Fiktiv Szczecin."
Many map authors do not bundle these assets to keep their own download sizes small, assuming players already have the "standard" Simple Streets library installed. If you are building your own map in the OMSI 2 Editor omsi 2 addon simple streets
Provides the specific layouts needed for tight city turns or wide suburban boulevards. The unified texture is efficient, but it is not 4K