I am building a 2x3 tunnel for rapid travel (via minecart) through the Nether. The tunnel, in cross-section, looks like this:
NN N = Glass N N X = Cobblestone N_iN i = Torch (alternating Redstone and regular torches, spaced out a bit) NXXN _ = Minecart track (alternating powered/unpowered)
I have read this question  and the prevailing answer there basically says not to mind the Zombie Pigmen. For me, that isn't an option because Pigmen can be a bit of a showstopper to minecarts in my tunnel.
They spawn in the tunnel, as opposed to walking into it (this seems to be consistent with the Wiki article on Zombie Pigmen , which merely says they can spawn at "any light level". They're a problem because they appear in groups of 2-3 and prevent minecarts from moving along the track.
I have thought of a few possible ways to deal with this:
Get off, pick up the minecart and walk around them, then put the cart back down and resume traveling. This is not ideal because I like to go AFK while on minecart tracks, and coming back to find I only traveled 50 meters before hitting a Pigman is frustrating.
Punch a hole in the glass and shove them out into the lava. Again, this involves getting off the cart, and punching a hole in the glass makes the tunnel temporarily vulnerable to Ghast fireballs (thereby defeating the purpose of fully enclosing the tunnel in the first place).
Attack them and move on. Not ideal because there is a good chance I will run into another gang of Pigmen further down the tunnel that will stop my cart and kill me while I'm AFK.
Make the tunnel slightly taller, and make a trench on one side (or possibly both) into which the Pigmen can fall but from which they can't jump back up onto the minecart track. I'm not sure how effective this would be, as I'm not sure they would voluntarily wander into the trench.
There's also this design, found in a Minecraft Forums thread :
N N = Glass _ _ = Track X X = Cobblestone
Nobody can spawn (or walk) on your track, and the glass also keeps you from attracting ghasts. It's very relaxing riding across the netherscape in the apparent open, watching ghasts fly about overhead unaware of your presence.
I haven't yet tested it, but I would hesitate to embrace this design, as it seems like it's an exploit that is liable to be "fixed" in any given future update. (I just re-did about 4 km of track that was previously powered by exploiting the minecart collision bug/feature, and I do not want to go through that kind of thing again.)
Is there any non-exploit, modless way to keep my tracks clear of Pigmen? I should add that this is in the context of SMP, and I don't want to turn
spawn-monsters off either.
I would prefer using half steps / slabs over fredley's solution. The are low in cost, and look nice in most situations.
The way to ensure no pigmen spawn on your nether rail is to place glass above the rail. This is not a bug/exploit and will not be “fixed”. Glass is a transparent block and will not suffocate the riders, but you will need to clear out any areas you may wish to exit the cart at. If you need a walkway, build it beside the track using slabs/half steps (assumeing you need pigmen not to spawn on the walkway; they would still be unable to obstruct the minecart track even if allowed to spawn on the walkway).
As to powering the tracks, I would actualy recommend levers over torches. They are hidden if you are not committed to glass on the bottom layer.
N NN NNN NNON X_X X_ON >XX >X-X > = Lever O = Air - = Slab/halfstep N = Glass
Since version 1.5, this hasn't been much of an issue, as that release introduced a rule in the mobs' AI to avoid rails unless they are chasing after the player. Although I have still found Zombie Pigmen appearing on the tracks, this is now not as much of an issue as it was in previous versions.
Zombie Pigmen are able to spawn on rail tracks, so removing the walking path on the side will do nothing. But as has been mentioned, adding blocks above your tracks will prevent them from spawning and help keep them from walking onto your tracks 100% of the time. This is a common "fix", and has been around for quite a while, and it doesn't seem like the developers have any plans to stop this fix from being possible.
The following blocks can safely be placed above the tracks, and will not suffocate you:
There are other blocks that would work, such as Beds, Chests, TNT, or Enchantment Tables, but I have excluded them from the list due to being impractical.
In my opinion, the simplest way to avoid pigmen spawning is to place top-slabs above the rails. You can still go through and quit the minecart.
For slopes, I just discovered that the opened fence gates above the rails do not stop the minecarts. Edit : after some tests, pigmen can spawn in open fence gates :-(
Use a lava trench instead of the regular torches instead for light. This will make one less space for the pig-men to spawn and there is a good chance they will accidentally walk in to it and kill themselves. The only (possible) problem could be is you inventory could get filled up with rotten flesh from pig-men who died on the tracks.
Set up a series of pressure plates to activate pistons that drop down over the track with another piston attached that push the pigment out of the way, then retract. It would be complicated and involved, but it should work, even for diagonal pieces.
I am having the same problem and it appears there is still no solution. I have found that using Worldguard provides limited help in staving off ZPN. You can make the tunnel a polygonal region that does not allow ZPN spawning. Issues with this idea are:
By far the best way is to have a design like this:
Minecart Track ontop of any block. The space above the minecart track should have a slab upside down. This means the pigmen can't spawn, but you won't be hurt going through the track.
AFAIK there are (as of 1.6.5) no ways to prevent pigmen from spawning in tunnels without exploiting the glitch you are referencing from the forum thread. Considering that the Nether now works for SMP this becomes a real concern, and I'm frankly a bit surprised that notch hasn't made it so pigmen can't spawn on rails.
Change the difficulty to peaceful. Zombie Pigmen don't spawn on peaceful difficulty.
1.0.1 -- still no way to fix this. Regarding the trench idea, currently ZPM will avoid the trench, but walk into it, and then try to jump out again when they fall.
A very easy fix would be to change the spawning conditions for light levels. Place your torches/glowstone along your line -- no zombie pigmen.