Got this one fixed for you. I installed some bridges where your main roads were intersecting your rail lines and moved your rail cargo hubs off of the main roads and round-a-bouts where they were causing most of your issues. All of your cargo hubs are still active and running smoothly. I also changed out three of your intersections for your highways and did some lane mathematics.

I left the game running for awhile with despawning turned off and, before fixing, your city was at 7% traffic flow, after making the above changes, you are now at 83% to 88% traffic flow.

Enjoy!

You can find my fix at:

https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2028685742

I fixed it for you, I had to disable the cargo train stations because they couldn't absorb all the traffic. Also, give timed traffic lights a try, you'll be able to get a lot more throughput using timed traffic lights instead of normal traffic lights.

https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2021367158