The latest SPUI is here, without traffic lights that once restricted its capacity. It is also optimized for the pathfinder. Local vehicles turning onto the freeway switch to the innermost and outermost lanes, while through traffic stay in the middle lane. Still, you need to plan carefully to handle the freeway traffic coming off onto the local roads. If all the vehicles choose to turn right at the next intersection, they will all line up in one lane despite two empty lanes on their left-hand side. 
 
Size: 50 cells across and 50 cells along freeway. You need to preserve its spot before plopping it in. I know it's huge but it's needed for the more gentle slope.
 

Recommended companion mod: Saik0's Toggle Zoning mod
--Disable the zone by the ramps.
--Usage: Open roads panel, toggle the button off, and then place the interchange. 
http://steamcommunity.com/sharedfiles/filedetails/?id=415782697 


 

Installation:
Subscribe to my Steam Workshop page to receive an update automatically.
http://steamcommunity.com/sharedfiles/filedetails/?id=414682041
 
Or unzip and move the contents to your local custom content folder.
Path:  [user]\AppData\Local\Colossal Order\Cities_Skylines\Addons\Assets

 
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This design was accomplished with the aid from following mods:
Japa's Fine Road Heights mod
http://steamcommunity.com/sharedfiles/filedetails/?id=413678178
Japa's Stricter Slope Limits mod
http://steamcommunity.com/sharedfiles/filedetails/?id=413311572 
 
Rollo's Terraform Tool mod
http://steamcommunity.com/sharedfiles/filedetails/?id=411095553