Is there a way to keep Zombie Pigmen off of minecart tracks in the Nether?

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.

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:

• Glass panes (I would really recommend this one, since they are "cheaper" than glass blocks, works with stained glass panes as well)
• Glass blocks (works with stained glass as well)
• Glowstone blocks
• Leaf blocks
• Iron bars
• Fences (of all materials)
• Half-slabs (of all materials, note that they must be single, NOT double slabs)
• Stairs (of all materials)
• Trap doors
• Pistons (both extended and retracted)

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.

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

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 :-(