The broken lines on either side of this roadway (in this case, lignes de rive) mark the edges of the roadway (very helpful at night). Drivers are allowed to cross the line to stop, park, or turn.
When I was taking classes to get my French driver's license (twenty years ago now!), I learned that marquages au sol (road markings) are very important. For example, a broad line across your lane at an intersection means "Stop," even if no stop sign is present. So you have to pay attention not only to roadside signs, but to what the markings are on the road surface.











