If you adopt the Parisian way, you can change lane very easily and quickly even if there is a big traffic jam. I have drive in traffic jam in smaller towns (like Cherbourg), it was more difficult to change lane.

The fact that you can not change lane without forcing is a normal consequence of the increase of the traffic. I think the unwritten rule is that people should not turn on flashing lights too early before acting. The better communication of the intents and a fair level of trust that other drivers will understand it (and not try to block you) makes driving a lot easier (in Paris).

> I think the unwritten rule is that people should not turn on flashing lights too early before acting.

A bunch of highly nuanced rules like this seems very fragile. If you are driving in this manner, you have a responsibility to be alert for things breaking.

The parisian way is resulting in a city with one of the highest traffic fatality rates in the world.

The facts show that whatever the parisians are doing is definitely the wrong way to do it, and should be changed.

The best way is, if someone signals a lane change, let them in.