your mod is very cool genius. but you can make a railway tunnel.

The original impetus for creating this mod was to create subways. Right now, you can only build some transit related entities underground (including rails, locomotives, and wagons) but I forgot to white-list stations and chests (will be fixed soon).

I thought about having a way to transfer entire trains between levels but so far have not found a good way to do that. There are just so many edge/corner cases when it comes to trains.

you are so cool !!!! thanks, I hope the mod will develop

until the devs create a method to combine a train and all connected entities into a single data-structure that can be transferred between surfaces, this won't be feasible. it's easy for undergrounds as the convert item "packets" into simple data and simply teleport them to the other underground after x-ticks (based on length and belt speed) but trains are different, and there is no way currently to convert a train and all attached entities and container items into a single data structure to be teleported across different maps. unfortunately :(
would love to have train tunnels in the game.

@usafphoenix : Just in case you ever see this thread again, have a look at this.

https://github.com/Godmave/clusterioTrainTeleports

Stringifies trains, sends them over the internet and parses them again.

wow (sorry for late response. never knew it got a response)
i guess someone did figure out how to teleport a train, although, not clear if it was done using the programming language the server clusterios use is based on, or if it was done in pure lua....

at any rate, never get the chance to really play multiplayer much. my mod folder changes four-five times a week as i test different mods. i usually scrap a save after a few days. want to do a mega base that would benefit from clusterio, but really don't think i have the time to invest :|

For this, I recommend the train tunnels mod: https://mods.factorio.com/mod/traintunnels. It is still buggy as it is really new, but works great for inter-layer trains