This video explains how to build a realistic highway with separated toll lanes in Cities: Skylines.

It shows how to set up the lanes, how to make connections between them and how to detail the build to make it look realistic.

The assets and mods I'm using are listed below.

Assets/Props:

Express Toll Lane Sign (Prop): http://steamcommunity.com/sharedfiles...

Road Decal Pack (6 lettered road markings): http://steamcommunity.com/sharedfiles...

Bike Middle (After Dark DLC)

Highway Barrel: http://steamcommunity.com/sharedfiles...

road barriers pack: http://steamcommunity.com/sharedfiles...

Concrete Median Barriers: http://steamcommunity.com/sharedfiles...

Realistic Merging Lanes: http://steamcommunity.com/sharedfiles...

Ultra low tri trees: http://steamcommunity.com/sharedfiles...

Mods:

Cgameworld Mod List: http://steamcommunity.com/sharedfiles...