I'll be happy if cars can drive down a 5 lane interstate, in a lane other then the far-most right lane.

It takes a ton of optimization to get multi-lane highways and interstates to be properly utilized... If I recall, I used traffic manager to only allow drivers taking the next exit to use the right lane, as the mechanics... are very finicky.

Edit- and appears, they heard the call.

Lane Usage

In Cities: Skylines II vehicles use more lanes. They try to optimize road usage to allow as smooth traffic as possible, occupying all available lanes as they travel to their destination. This means that if one lane in a multilane road is filled with vehicles waiting at the traffic lights, new cars arriving at the intersection choose the other empty lane(s) to fill the intersection evenly.

On multilane roads, vehicles can overtake slower vehicles when the simulation notices that the other lanes are less used. Vehicles also switch lanes to avoid completely blocked lanes due to a traffic accident, a traffic jam, or a stopped vehicle, such as an ambulance picking up a patient. Additionally, vehicles will try to give room for the emergency vehicle by switching to other lanes when possible.