During a visit to Italy recently, I noticed that the speed limits applied on 3 lane Motorways in the Milan area, were sometimes indicated for each lane, instead of just one and the same limit for all lanes !
For example, the speed limit for the "Inside lane", (normally for lorries), would be 60, the middle lane for local traffic would be 80, and the outside lane for faster cars, would be 110 or 130.
In spite of the heavy traffic, all the vehicles seemed to move forward constantly and there was less "lane hopping" ! Traffic jams were thus definitely reduced.
Other countries might benefit if they tried this solution !