I was thinking of having the setting be in some sort of seperate dimension, largely a desert in all directions save for large but ramshackle towns that have built up around areas where there was something of worth to people. These towns would be spaced VERY far apart and the desert sun extremely hot and oppressive, far too hot to be out in unprotected during the day (Which lasts for several "days" at a time. As such, transport is done via various types of railed vehicles, trains.

Now an interesting slant I was thinking on top of this would be to fiddle with some physical universal rules; a problem with trains is that they follow tracks but what if the track always went where you wanted to go?

I was also thinking of having the trains be solar powered, running at tremendous speeds if they are fully functional and under the sun but grinding to a halt (Or near halt if you have some sort of energy collection systems) in the long cold darknesses that sometimes occur. Several things could possibly hook into this.

What do you think?

>>7708687
sounds ok, not sure about the magic tracks though

try playing Legend of Zelda; Spirit Tracks for some ideas... basically, the entire world is covered in train tracks which are actually chains which bind a demon god.

A while back some guy was on talking about his idea for a setting. It was a post-apocolyptic disease type of thing, where the only safe areas were the network of trains that had been built before the Collapse. So now mankind had to live on the massive trains that thundered around and around.

It sounded pretty cool.

>>7708737
Yeah, I'm not particularly taken by the track idea either but I simply can't think of another way to make trains work in this way, if they're not on tracks then they're trucks really and if they are on conventional tracks..well.. there's a whole lot of logistics involved in avoiding collisions/ tracks not going where you want etc etc.

>>7708457
i am going to have to dig, but years ago (2nd ed D&D at least) they had a book of marvelous inventions, including, tada, a train. the thing i liked about it most was that it was a struggle to get the whole thing going. You had to lay track and feed the demon in the boiler, etc... with STEEP initial layout costs.

Look at the berron game settin gfor DnD 3.5 and 4th ed. It has magical airships, trains and what-have-yous as well as war, intrigue, elves and a whole lotta other shite. The theme with Eberron was "If it can happen in DnD, it can happen in Eberron" so theres plenty of play area for you to have whatever campaign you guys wanna play.

Here it is:

The Book of Wondrous Inventions (AC11)
"Have you ever wondered why, in a world full of magic, there are no enchanted labor saving devices? Few magical modes of transportation? No bespelled byproducts of the inventor's art? Wonder no more! They are all here, in this latest compendium from the Game Wizard's lair: The Book of Wondrous Inventions!
The Book of Wondrous Inventions is useable with both the D&D and the AD&D game systems. Each invention is clearly outlined, including function, form, and hazards of use. Statistics and spell details are are presented in a manner compatible with both game systems. Adventure scenario suggestions are given, as well as design instructions for characters who wish to build duplicate device.
As an added bonus, a section is included which details a system for creating spells and magical items. This will prove especially useful to players and DMs who use the D&D game system; the detailed information is also of help to AD&D game players."

1987 ... 96 pages ... TSR 9220 ... ISBN 0880384972

Post apocalyptic setting. The only things to survive the nuclear war/zombie invasion/deadly virus/whatever were several dozen huge armoured trains, large enough to hold the population of a small city. They continue to grind around their tracks to this day. Some are empty (of their initial population, who knows what's moved in since?) and present tempting targets for looting. Others contain active communities who will seek to enforce their will upon those who scrape a living in the ruined wastelands.

>>7708895
A lighter twist could be fro the Thundarr the Barbarian episode where lizardmen were using the train they had captured to haul their "death lotus" harvest back to their lair. The flowers were then converted into a gas which could be shot out of some sort of gun, rendering victims into zombie-like creatures, vulnerable to their bidding. Ookla! Ariel! Ride!

Have you read China Mieville's "Iron Council"? It may have an interesting idea for you, as it has one interesting train hijacking take place.

Essentially a train line was being pushed across a continent by slave labor. The labor camp is centered around a big train that carries all of the supplies for continuing the construction, huge thing. Slaves get pissed and steal the train, and the tracks. The build the tracks to go wherever they want, and rip them up behind themselves. They've been doing it a while, so they're good at it. There might have been some magical shenanigans involved to make it all work so well, but I forget really. It's kind of a steampunky book, but it's still a fun idea, a train that picks up it's tracks behind it and all :D

rolled 2, 4, 1 = 7

The trains don't just sit on the tracks, they're attached to them. Extremely high winds and frequent storms out in the barren zones make it impossible for most vehicles to stay on the ground, let alone move in a straight line. Only the trains are massive enough to use gravity anchoring, and as long as they're on the tracks, they'll end up where they're supposed to.

eternally moving train
running between night's merciless coldness and day's scorching heat
holding the surviving population of the planet

and then a message
from the train
runnning between day's scorhing heat and night's merciless coldness

>>7708985
Good idea, I like it.

I'm liking all the other suggestions too, the track laying/pulling train sounds good perhaps for a special group in the setting.

>>7709057

And as far as the stolen train goes, I think they eventually ended up running train back to the city state and waging a civil war, but I forget how it turned out. I always imagine them pointing the huge train at the city and just sort of crashing into it full bore :D Like when they smash a driverless car into something in the movies, but bigger with more exploding boilers.

I think really the biggest problem is getting around, the "tracks that go wherever you want" WORKS but it's somewhat akin to using a hammer and nail to staple two sheets of paper together and while there could be a train that lays and lifts it's own track that's sort of beginning to only "technically" be a train, if you get what I mean. I like the idea I just don't think it's quite right for what I'm after.

rolled 6, 3, 3 = 12

>>7708985
The trains are also, as expected, partially powered by the omnipresent winds. Gigantic turbines spin with incredible force as the insane weather forces air into the scoops, generating the energy that keeps everything on board more-or-less peaceful. If the wind ever stops, the train goes to auxiliary power, most of which is used to keep it moving. It can get very dark, very cold (or hot), and very unsanitary if the train is without its main power source for very long.

rolled 1, 3, 5 = 9

>>7709180
So why doesn't the train just stop until the wind picks up again? Well, for one, timetables. When the trains don't run on time, bad things happen. For another, you really, really don't want to be sitting still out there, storms or no.

>>7709180
Again I am liking this very much, fleshing out the actual idea of the train units themselves.

Ok, how about this, the desert is literally riddled with tracks and junctions which were there BEFORE people arrived in the area, the junctions and sidings and everything are all controlled remotely, presumably by some sort of calculating device setup by the original track layers. This device does not have direct control of any of the trains but does monitor them silently and ensure that they don't meet, opening up paths to avoid eachother etc etc. Again, this could provide many plot hooks to a game in the setting perhaps?

The trains, so they say, can go anywhere.

Problem is, sometimes that's exactly what they do. You'll be on a routine trip and there'll be a little shudder, and if you've been riding long enough, feel the train turn where there shouldn't be any track.

In a few minutes, the trains slows and stops. It's always at a proper station, maybe one far away. maybe at a place that's old and wrecked that no-one's ever seen before. The train stays a few minutes, and the more adventurous passengers leap out and go running. They'll look for a map to point out where they are, or something valuable to salvage, or just to see the sights.

Sometimes they don't come back. They disappear or dally to long, and the train leaves without them, moving by itself.

Sometimes, something gets on the train at these stops.

rolled 3, 2, 3 = 8

>>7709281
The Conductor is the brain of the tracks. The face behind the mask, the master of the madness. It's a machine, a very old one. Its tendrils stretch thousands of miles in every direction. Monitoring. Sensing. Opening routes here, closing routes there. Signaling for repairs when a track is damaged. Calling for a tug when a train stops. It does it all, automatically.

And it hates it.

Did you ever play Transarctica? A world in eternal winter so almost the only thing that can cross the snow are huge trains. Cool battles between trains travelling on parallel tracks, or pirate ambushes.

Hi, how's it going?

Ok, so thanks to our Subprocessor DM here the travel via rails problem is largely solved, we have an ancient network of rails maintained by the mysterious Conductor, systems such as the sun, weather and distance which makes using these rails a necessity to travel from city to city and the notion of needing to KEEP moving once out on the rails or something bad will happen.
Very good, you've helped me immensely all of you.
Anyone have other ideas?

>>7709516
Rail Tracer, a monster that eats train passengers

>>7709559
Ohh, something sinister using the tracks and conductor itself...I like that..it raises several questions for players too, why does the conductor allow it to come into contact with trains? Does it take local track control FROM the conductor perhaps?

Ancient civilization left tracks between stars and then left, died out. Now our intrepid explorers will ride a train through the cosmos!

Ghost train comes and goes on the same empty track on the outskirts of a dieing rustbelt town in mid america. And when it does earthquakes, typhoons, and assassinations increase world wide. Follow our team of super sleuths through an ethereal mystery ride!

In a world where all land mass floats around the decays of a neutron star the operators of the air trains operate the most powerful cartel. Different track clans vie for power in this game of international espionage!

rolled 3, 3, 5 = 11

>>7709516
Well, if you have gigantic, massive trains crossing hundreds of miles of desert to reach isolate population centers, what do you have inside those centers? Mini-trains and subways, right?

rolled 6, 2, 6 = 14

Trans-Desert trains must be heavily armored and are almost always heavily armed as well. Just because humans can't survive for long out there doesn't mean nothing can. Offensive weapons of choice are large-caliber "shotgun" turrets and flame guns for close-in defense. Most trains also mount a several-foot-thick Gravecatcher to clear the front of the tracks.

If your players aren't too familiar with The Dark Tower you can steal an idea from it; Namely Blaine the Train.

As old as time, the A.I/Magic train is self-aware. Due to long isolation its gone slightly mad, with a suicidal bend, just running the same course back and forth every day without any passengers.

Then, in an attempt to flee from something terrible, your party boards the train. How does this mad old self-aware train react? What obstacles does it throw in the players way to either kill them or keep them?

Preferably not riddles.

>>7709613
Subways in population centres could be more mundane constructions though, not connected to the Conductor and working on simple timetabled rotation of cars. Perhaps that actually annoys the Conductor for some reason?

>>7709681
Unfortunately I know for a fact that they have all read the dark tower as my copies have rotated around the group at least twice now! Haha.
Still, it's a good idea to build upon.

rolled 3, 2, 2 = 7

Warfare between city-states, rare as it is, is also carried out by trains. Long-range weapons capable of striking distant targets are almost non-existent, as unpredictable desert winds throw projectiles off-course and electrical storms render missile guidance unuseable. Thus, to wage a war you have to get close. C-Trains, armed with heavy guns and unguided mass-fire rockets, get as close to enemy stations as they can and unload, crippling the city's transit capability and opening holes in the local defenses. After that, the desert itself will begin to invade, and more often than not, the defeated state will surrender and request assistance, rather than see its population overrun by the marauding horrors.

Mysterious lights and silhouettes of trains that match no common design can sometimes be seen in the distance, travelling at speeds for greater than even the lightest high-speed unit can match. Though many report seeing them on the tracks none have seen them stop at a station and the Conductor denies knowledge of their presence (Assuming of course that the Conductor can be queried in some way)

rolled 4, 1, 1 = 6

>>7709726
The Conductor was designed and built as transit-master. It is programmed to control. It needs it. Over the centuries, its systems have degraded, and its control has been steadily eroding. Now, there are entire cities, entire swaths of desert where its touch is unfelt, and unwanted. This, its old circuits cannot bear. Though it hates, it cannot uproot its programming. And so it wages silent protest against the usurpers, trying in vain to regain control.

rolled 2, 4, 2 = 8

>>7709865
The Conductor knows all, sees all. Though its power is constantly growing more limited, its eyes are more powerful than ever. The very idea of something escaping its notice is unthinkable to it, and it denies that this is even possible. There are no trains but the ones it sees. There are no others. There can't be.

>>7709924
Rail network failure could be worked into it as an extra risk of long-distance travel then, assuming that the Conductor has some for of basic autonomous repair (Though taxed to it's limit and slowly losing to the tides of time and wear) dead spots of track could come and go around the network.

Megalopolises in a vast, barren wasteland are connected to each other by a series of railways; massive trains roll from one city to the next, providing a quick and efficient means of trade and transportation that allows to city-goers to avoid exposing themselves to the harsh elements of the wasteland. The problem is, however, that these elements occasionally encroach on the rails, damaging the infrastructure and causing chaos for the megalopolises. As such, it becomes necessary to recruit soldiers, mercenaries, and so forth to guard the rails from anything that might threaten them.

>>7708687
Desert so hot no human can survive for long? Boring.

Make it so that there are tribes of bandits that live in a vast system of caves and caverns near the tracks, they can't come out during the hottest part of the day or the coldest part of the night, but during the twilight hours where the conditions are favorable for human life they are forced to prey on any passing trains for supplies, for this is the only way they have ever known and they have their daughters to think of.

rolled 3, 2, 5 = 10

The world is an old, old place. Many of the cities are built on ruins, which themselves are built on ruins. Only the very newest settlements boast a foundation less than five decades old. Once, when the world was younger, a great, subterranean network linked all nations, but it has fallen and collapsed. Only the surface tracks are used now, with the Underground barely a memory. If it could be accessed, far beneath the cities of modern day, the treasures inside, both in technology and resources, could bring about a new age of discovery.

rolled 3, 5, 3 = 11

>>7710010
That's a good idea. The greater the distance traveled, the greater the chance of a fault. Though the network is extensive, detours can take you far out of your way, and if there is a damaged section between you and the next junction, you better hope the Yardmen won't be long.

I'm stunned, you guys are really pulling this together into something I am loving the sound of, I hope you're enjoying sharing the ideas too, I wouldn't want to seem ungrateful.

>>7710038
True, that is a little boring isn't it but it needs to be critical that the trains are basically the only way to make it. How about the tribes have water suits or something that allows them to operate on foot or perhaps mounted for decent lengths of time in the sun?

rolled 3, 2, 6 = 11

>>7710122
Sounds a bit like Fremen. Perhaps they have their own little secrets. Chain-anchors to keep them grounded. Underground bunkers, long-abandoned, sunk deep into the rock that most can barely scratch. Trained beasts, as such that roam the wastes, thought to be untameable. Lost arts, relics uncovered in exposed sections of the Underground. Burrowing camps that move beneath the sand, forever moving ahead of the storms.

They needn't all be the same. Different group, different quirks.

Alright, I think the general rail network and related stuff is pretty fleshed now, how about WHY is everyone here?
Is there something in the sand that they are collecting? Mining operations for some sort of material which is easily found here or scavenging for old tech left by whoever built the original cities and tracks? or is it something else maybe?

>>7710122
If you were to consider that the days and nights were longer due the world turning slower, there would be a much longer "cooler" period in the "morning" and at "dusk" than we on earth experience. This depending on the length of the day cycle could last anywhere from 5 to 12 hours at dawn and 2 to 8 hours at dusk with about half of the cool period before sunset and half after sunset on the dusk end of things. The trains should also be long and relatively slow to allow for time to be heard and boarded, the Desert Bandits don't know when the next train is coming and need to hit all of them, if able, for supplies. You could also make the trains deafening on the outside but soundproofed on the inside.

As far as mounted go, there are plenty of creatures that could live in a desert environment and be domesticated but they wouldn't be out and about around midday.

Necessity is the mother of invention as far as a water suit would go. I think it would be nice if the Desert Bandits didn't know for sure if the cities existed or not. And above all they should be human, they should feel terrible about what they have to do but they have to take care of their families and tribes and can't listen to the lies the men in the thunder boxes would tell them to dissuade their actions.

Didn't China Mieville write a novel about an anarchist railroad construction crew that builds tracks to where they want to drive their train?

rolled 3, 3, 4 = 10

>>7710283
They are here because this place exists. It is habitable, though not very comfortable. Their fathers fell from the sky when the planet was green, and now they are here, the children of the originals, keeping watch over a world blasted into oblivion.

Resources are abundant if you can mine deep enough. Lost technology is everywhere if you know where it's hidden. But mostly, everyone here is just trying to survive the next day. It is rare for a person not to think of leaving this planet, just as it is rare for a person to discover the means to depart.

>>7710340
see
>>7708970

>>7709924
This gave me the image of a large construct - the body long - with many thick, hard-steel spiderlike arms which roams around on the tracks. They occasionally "crawl" over the trains on their way to fix faults. They're considered off-limits by the cities as they're the machines that fix the tracks, and every year it seems we're seeing fewer and fewer of them...

>>7710340
Yes except it was about communism, Mieville being a real-life Marxist theorist.

rolled 6, 4, 3 = 13

>>7710398
The Yardmen were once plentiful, swarming over the tracks day and night, clearing obstacles, making repairs, shining things up a bit if they had the time. Now they are few, and stretched thin. The great, booming factories that produced them have fallen silent, and been lost to the encroaching wastes.

Yardmen are the Conductor's hands. The autonomous workers that keep everything running. Once, they were standardized, clean, fast machines, even able to speak on occasion. Now they are patchwork, lumbering, slow monoliths, creeping along on borrowed limbs and splintered tracks. They are dying.

>>7710283
The cities have been aware for a long while now that the A.I that runs the train system is breaking down. Just prior to the game, an unheard of event occurs. Two trains collide in the desert, thousands are killed.
Assembled by your City-state, your party must find The Conductor and try to discovered just what is causing this catastrophic loss of planetary cohesiveness.

rolled 4, 1, 3 = 8

>>7710513
Only problem is, no one knows where the Conductor actually resides, or even if it's a single entity at all. And, naturally, no one has the security clearance to ask it anymore.

>>7710513
>>7710572
Perhaps the long isolation of a seemingly highly advanced AI has caused problems within it's systems, perhaps it invented selves to talk to and they've gradually used up more and more resources inside the system. I like that the Conductor would be killing itself to keep itself from being lonely.

>>7710668
I think you have your plot seed involving Trains.

rolled 5, 1, 1 = 7

>>7710668
The Conductor is schizophrenic? Yeah, that's great. That's just perfect. You better make sure the PCs remember to hit the 'hard reset' button on the way out.

I just had a huge post of fuckwin about the planet being a forgotten mining colony that was left to die after an asteroid kills the planet's moon and Corporate Earth, masters of efficiency, deem the venture either too costly or too risky to make rescue efforts to the planet. Been so long that only the Conductor knows the truth of the origins of man on the planet for sure. But 4chan ate it.

>>7708457
Shit yes, trains! See, we've colonized a new planet, but the terrain is ungodly bad. Wouldn't be a problem, except there are few waterways in the area and the atmosphere is too thin for air travel. Narrow-gauge rail to the rescue!

ITT the OP goes to the next session with the most fucking awesome idea any of his friends have ever heard before. Discuss.

>>7710820
Sounds like it would have been good, shame it was eaten.
Perhaps it was too good...

/tg/ this is an awesome idea, I love it. I particularly like the idea of warfare between trains, perhaps consider a wind singer like situation, where trains deploy carts with sails from torpedo like tubes. These are either piloted by elite soldiers for boarding actions, or full of explosives to damage the other train.

rolled 4, 2, 2 = 8

>>7710820
The Conductor is aware of your presence. The Conductor will not allow any further incursion. Obey the Conductor.

>>7710867
Pretty much, yeah. Trains are awesome.

OP, whatever you do make sure you always imply the Conductor is a person so you can pull a "Yes, I'm President John Henry Eden." moment when the PCs realize the BBEG is a button.

Another reason for the trains is the high gravity of the world. Despite its massive size, the lack of an iron core reduces its mass enough to have about 1.25G with significantly more surface area than earth. This lack of an iron core is also why humans can't be out during the day, the thick atmosphere protects during twilight hours but high noon is fatally radioactive to non-native life. Many settlements are not cities, but warrens, dug into the earth to save themselves from the horrors of the surface. Water is not in short supply, although not nearly as abundant as here. The perpetual band of fog that moves along the twilight zone is enough to maintain a dense shrub that keeps the soil in check, allowing the rails to survive for so long unburied. The great herds of cow-like beasts that move around the largest continent have evolved to avoid the tracks, instinctively knowing how to avoid the conductors wrath. Some tribes of outlanders use the hide of these beasts as shelter during the day, the shell-like scales naturally block the deadly radiation. Not all life avoids the tracks though, a few mega-predators have specifically adapted to tearing open passenger cars to eat those cowering inside.

Well I'm afraid I have to leave the thread now but the help you've all given me is immense, it's as much your creation as mine so I'd encourage any who want to to continue making it better to do so by all means.

Thank you all!

This should be archived, it is fuckawesome. I'd do it myself but I'm too retarded to know how.

I'm archiving it now

Done:
http://suptg.thisisnotatrueending.com/archive/7708457/

Needs more trains.

I've been pondering a series of train-based sessions for a D&D campaign. There haven't been any railways before now, so rather than just retcon in some steam-based empire the players didn't know about, I figure the way to do it is put it in the Underdark.

The Svirfneblin (or some other deep race) built the network to connect maybe 3 or 4 major cities. Over the centuries, warring factions have made large stretches of the tracks unusable, others have been rebuilt and expanded by Drow slave labor. The player manage to come in possession of an engine, and will need to figure out how to make it work, and get where they need to go. The blackened chains with runes of Elemental Binding ought to be a helpful first clue.

Pic related. Deep Crow attack en route is a given.

Sorry if I'm necroposting, but having just read (and falling in love with) this thread, I have a few things to add.

Of course, the naturally barren and hostile environment can be overcome with the right technology, and preparation, and besides bandits ON FOOT would be completely unexpected in the eyes of the conductor and the city-states.

2) The other danger lies under the surface. I'd recommend mechanical "Screamer" drones (automated mobile buzzsaws from former superwar), Graboids (Tremors?) or Antlions live in the wastes. Ancient machines and barriers keep them away from the cities, or maybe a natural predator response to pick on the weak & isolated keeps them away from the city centers. Maybe they damage the track with their burrowing. . . Maybe they are a greater threat in the sprawling underground ruins, where they roost. . .

3) trade by rail is important now. Being wartorn, this world is hard to live in. If you can't fight and take what you need, then you NEED to negotiate and trade with the neighbors just to survive. Social faux pas, and diplomatic 'incidents' may be severly punished, as killing the trade council is a bad idea. (Sure they're jerks, but they are the lifeblood of the city.)

Mail. Mail is traded too, as intel is a GREAT asset. . .as is cartography and mapping of new/repaired/destroyed rail charts. . .

The conductor runs the rails, but some enterprising humans have been studying in the shadows (Mercenary? Former Government? Anarchists?). . . They are learning to hard code the massive engines to respond to human operators. They have signal device to relay commands to the rail relays. . . They can CHOOSE their route, and this power can corrupt. . . Any power in the wrong hands. . .

If the factories for the Yardmen, cars, or engines is ever discovered, use the movie 9 as inspiration. Black, soot and smoke belching, dangerous exposed machinery, designed for efficiency, not operator safety. . .

Missions. . . Maybe the trains need fuel sources. . . Coal can be dug, wood is rare (But effective?) The ruins may have stored power cells and working solar cell charging stations. . .These are guarded religiously, maybe even by a religion. . . The sun god powers our trains! (through charged batteries. . .) Superstition is high, because in the absence of knowledge of their technology, people grasp for answers. . .

If the factories are restarted, maybe they can't be shut off! Too many trains strains the already stressed conductor system, systems glitch. . .

Maybe the ancient powers that be (off-world humans) send a long range ancient radio signal, received by the conductor, updating his system software . . . Interrupted by interference. Truly ancient.

Air- fishing. . . . The trains pull parasail - style nets behind, catching the flocks of gulls and desert scavenger birds that follow the trains, providing a staple of food for the patrons, where meat is rare. . .
Also for food plants, rarely will there be a Hydroponics car, with sunlamps, and biochemically treated soiled. NO Human access admitted. . . Of course rules are fun to bend. . .

Ancient ticketer system. . . Robo-bodyguards that used to receive payment from rail-clients of the various companies and nations in charge. Though mostly defunct now, they have been watching and waiting and counting the vagabounds and freeloaders. Suddenly, their uplink is restored, and massive economic crash (if a credit-based society) as the computers automatically deduct ancient currency out of accounts, turning off power to many parts of many cities! PC's have to fix that Immediately!

This reminds me of a short story I wrote a long time ago. No dialog, about a frontier town in the middle of the desert with rails running through it. No trains had come through in so long that people had forgotten what the rails were and nobody even knew there were other towns because they were so far away. One day a train comes through and one of the young men of the town gets on, and the train goes far and through a bunch of different terrain types all the way to the north pole where there's a big old observatory with an empty launch gantry in the middle. There wasn't a whole lot of point to the story but it was fun to write.

http://www.abandonia.com/en/games/635/Transarctica.html
Relevant DOS game.

Ok, alternate to sci-fi: High Fantasy trains.

The world has ley lines, and the trains run on these lines. It takes a trained mage to keep them on the right line, but the line itself provides most of the power. They run a few feet above the surface, held up by the power of the lines. Some trains are more like streetcars than trains propper, but most cargo is carried on larger trains because they need only one driver.

Trains are usually constructed mostly of wood, since it's cheaper than other materials.

The ley lines move unless they're held down. They're held down (where people care to do so) by iron spikes driven into the earth.

The anchored routes are privately owned and there is a charge for using them. While travel is possible off of them, it is dangerous.

An un-anchoured route can lead a train to Underhill before you notice it. The parts of Underhill most close to the prime material mirror it to an extent, so the transition may not me noticed. Underhill is partially co-terminous with middle earth, but not everywhere, and not always. Underhill is much larger than middle earth, and is also co-terminous with other planes. Any ley line that leads into Underhill will lead out again, eventually and somewhere.

Plane to plane trade via underhill is very dangerous, and very proffitable.