"This image depicts BloodyPenguin's Double Track Cargo Station ( https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/comments/703597323 ) used as both "sides" of a Cities:Skylines rail import/export hub, allowing a single depot to service both an internal and an external rail network, while still keeping the traffic of the two networks segregated.

The Double Track Cargo Station can both receive and send cargo on the inner tracks (as with a regular/vanilla cargo depot), but the outer tracks can only send cargo.

By connecting both internal and external networks to a single side of the inner tracks (and ignoring the other side) this configuration allows the depot to:
- receive cargo from any point on either network
- send cargo to any point on either network
- while still preventing the trains from *directly* passing through from one network to the other.

Incidentally, the above configuration should also work with a regular/vanilla cargo depot.

As a bonus, since the Double Track Cargo Station has a second set of tracks, by connecting to either side of the outer tracks with one-way tracks leaving the depot, extra trains can spawn to carry cargo outbound from the depot, while still preventing pass-thru.

This configuration fixes an problem with the previous configuration I had suggested ( https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1281627039 ), wherein trains would arrive at the depot and unload their cargoes (as expected). However, if they took on a replacement cargo, they would immediately despawn, as they are unable to exit the depot."