Warning - this is long post and full of new ideas
No commitment to do it, just asking for opinions, if this may be the way to go?
It is nice to see the discussion about pipelines revived. On Czech forum I had encountered requests also for cable-cars (or funiculars) like this one: http://www.lanove-drahy.cz/fotogalerie/nld_kuncicefoto.htm
or this https://en.wikipedia.org/wiki/Gondola_lift
I think these share some common features with conveyor belts and pipelines, and could be implemented as special type of way.
- the way is tightly bound with the used vehicles, their cargo type, capacity and speed. You cannot just change the gondolas to bigger ones. You have to change the ropes, build stronger pillars, install more powerful engines, ...
- stations, depots and engines are combined into one building, and are (usually) at the ends.
- there are no switches, crossings, etc. Just straight point-to-point connections. If necessary, one can do it by building a transfer station, where more lines meet.
- lines have limited length (rope length, pump power)
- can be elevated (cable-car), surface/underground (pipeline), surface/elevated (conveyor belt)
- all vehicles are in fixed distance and move synchronously, (un)loading is done quickly during the movement.
- the number of vehicles is given by the length of line. (2 vehicles per tile (there and back) - with capacity scaled with tiles/km in experimental)
- goods flow (mostly) in one direction - exception are passenger cable-cars/escalators - one-way line would mean allowing only empty vehicles in one direction
- downhill and uphill (partially) negates each other. If a line goes up and down hill in one stretch, the gondolas moving downhill, help to pull those going uphill. Similarly fluids flowing downhill help to suck the part going uphill, and if the outlet is lower than inlet, it will flow by itself (viscosity may affect this though). There will be defined power demands for straight, up, down (double/half) tiles, capped with maximum power of the engine. (Downhill could have negative power demand) If max power (or max distance) is reached, line has to be split in two - new pump.
- conveyor belts are clearly only for bulk goods, funiculars for bulk and passengers, and pipelines for fluids.
- fluids in pipelines can be abstracted as special vehicles - big drops moving there, and empty bubbles back.
- this will preserve the behaviour of goods transferred by other vehicles
So how it could behave in the game?
You open a new pipeline menu - you see a few ways. They have defined - type (surface, elevated, bridge, tunnel), subtype (cable-car, pipeline, conveyor belt, escalator), max capacity or weight per tile (km), max speed, max length, one-way or not, power/friction for up/down hill.
First you build the line, ideally you could connect surface/tunnel/bridge/elevated sections as usual, just limited by total length.
Then you build the end stations (and depots at the same time). Each subtype (cable-car, pipeline,...) will have its own station/depot.
Station part will behave as normal station - has defined capacities for pax/mail/goods, and could connect to other stations, have the same coverage as other stations.
Depot part will offer to buy a stationary engine/pump and gondolas. It may work as if building a train, but you will be allowed to build only one or two engines (one for each end) and so many gondolas as is the length of line. For pipelines and conveyors imagine that gondola is a bubble or blob
. There may be more types of engines and gondolas for each type, and the depot window will let you build only those that are suitable (max weight/capacity) for the built line. If the engine is underpowered could be show, just like with trains. Where applicable the gondolas could be of different type (pax/bulk). For pipelines / conveyors a switch for one specific cargo would be needed - cannot mix crude oil and gasoline in one pipe.
Then you just click start (no schedule needed) and see the gondolas appear on the line and move. In a pipeline you could see drops of oil moving. (So it won't be so boring). You could stop the line by sending it to depot. Perhaps a speed knob might be useful to avoid running half-empty.