Patrolling Elite stop method
Associated movies
In this method you get the bridge's patrolling Elite onto the near right ledge and use him to stop you from bouncing off when you fall from the V. From there you can move along and drop down at a safe spot of your choosing. Suitable only for PAL.
Full description
On the lower deck of the bridge there's a patrolling Elite with a plasma rifle. Regardless of difficulty level, he always seems to be red. Get him into rage mode so he'll come after you to try and whack you, then dodge his swipe at the corner of the lower deck so he falls off towards the near right ledge. I find it necessary to be right on the edge - a somewhat precarious position - else he won't get enough distance to land in the right place. The dodge is pretty easy, and even if you misjudge it and get caught by a glancing blow it's unlikely to matter.
If he lands on the apex of the chevron feature, he's likely to survive and slide to a stop at the edge of the ledge, though occasionally I've seen him teeter over and fall directly down. If he lands more than a couple of metres beyond the apex, he's more likely to stop short of the edge. In general, it looks like he needs to hit the chevron anywhere from the centre to about halfway along the far half, else he'll either die on impact or slide off. I wouldn't rule out freak exceptions though.
Assuming he has a good landing, get to the bottom of the V. Actually you could be on the V even before he's landed on the ledge, by running off the deck as part of your swipe dodge if you want to do things fast.
Run off the V almost parallel to the cliff face, and bounce off the friendly sloping chevron to then get stopped on the ledge by collision with the Elite. Typically you'd want to hit the apex of the chevron if he's directly opposite it, as commonly happens. There's no need to crouch as you hit the chevron. After killing him if desired, you can move along and drop down at a safe spot of your choosing, as described elsewhere.
It can be useful to have a plasma pistol with you to quickly stun the Elite after you've collided, but rapid fire from a plasma weapon or AR would probably do just as well to keep you safe. He'll already have so little health left from when you put him into rage mode, he'll die almost the moment his shield is gone. Actually you may not have to do anything, as he might go off the edge. There are various ways to cause that, some of which you can see in BCM29. The collision alone can be enough, but his footing is a factor here. He may already be partly off the edge, and when he rotates to keep facing you he may lose his support. If you give him a thump, so much the better.
A few tips. On Heroic or Normal, a good way of getting him mad is to take down his shield with a plasma ball then give him two frontal whacks. Works nearly every time. On Easy make it one whack (sometimes it'll kill him though), and on Legendary three (which can be hard to do because he can recover from a whack fast). Ideally you'd want to be pretty near the dodging point when you're doing this, so you can quickly run there and be under cover before he hurts you with his plasma rifle. There's a strategy for this in the section on checkpoint considerations. When he goes into rage mode he mustn't have a line of sight to the drop-off point, else he's liable to just stay where he is and shoot at you. You must ensure that he has to come around the deck brace to get a sight of you - at which point he may briefly fire but will then take a swipe.
Note: If you only take a glancing deflection off the Elite and end up going off the ledge, you could still survive if you get sufficient cushioning from the cliff face, or possibly a rock. Another variation on things is that it's possible to end up stopped on the ledge by a direct collision with the Elite, rather than bouncing against him via the chevron. He can provide enough cushioning. However, survival would be very fickle.
Checkpoint advice
Getting the Elite onto the ledge is the hardest part and is likely to take several tries or more, especially if you're new to the method, so it's good to get a checkpoint to minimize how long each try takes. Here's a specific routine I developed with that in mind. You can see it in action in the first part of BCM29.
Save the pre-bridge checkpoint so you'll always be able to restart from there if anything goes wrong. Kill the four sleeping Grunts and two Jackals, bypassing the patrolling Elite for now (tip: avoid stepping on the glass panels, in case he shoots them from below). Likewise kill the next lot of sleeping Grunts plus another two Jackals, and destroy any Banshee. Avoid triggering the bridge checkpoint until you've completed this elimination work. There are another two Grunts beyond the trigger line if you want to kill them too, but there's no need yet.
Once you've triggered it, keep it delayed and return along the bridge. Try to get beyond the Elite without him realizing. Ideally he should be on the lower deck (you can potentially draw him down beforehand if he's not already there), in which case you'd be taking the upper deck, but things can also work the other way around. If you are going along the upper deck, you can help keep yourself unseen by moving along the thin central strip between glass panel areas, which may or may not be holes by now. Eventually you could drop to the lower deck through a panel (shattering it is ok). On the lower deck, hide behind one of the ramps at the far end and get the delayed checkpoint. That shouldn't be a problem, as long as the Elite still isn't aware of you.
To make an attempt at getting him down, fire a shot or two to attract him in your direction, then when he's close (watch your motion tracker), move out from cover and use the 'stun and whack' technique to get him mad. Without waiting for him to start growling, run to the drop-off point and get into position. Because you're quite close, you should be able to make it to that sheltered position with little or no plasma in the back, a serious concern on Heroic or Legendary.
When the Elite is on the ledge, preferably get another delayed checkpoint at the bottom of the V, having gone back to trigger one in the exit passage after killing a few more enemies. You'll then be ready to make multiple attempts at being stopped by the Elite. But it's pretty easy, especially if he's opposite the apex of the chevron, so it shouldn't take more than a few.
Difficulty and system differences
This method may sound tricky but I'd say it's surprisingly easy. The main difficulty lies in getting the Elite down onto the ledge. It might seem unlikely that you could get him to hit the ledge in the right area, which is fairly small, but the way he goes off the deck is reasonably controllable by your position on the edge of the deck. Once you have the general knack, you may be able to get him onto the ledge with something like a 20% success rate. The subsequent fall from the V to get stopped by him is relatively easy, though it could certainly take a few attempts. It would be no worry at all if you've got a checkpoint beforehand. If you were to try the whole thing fast without bothering with checkpoints, it might take about 10 minutes per success on average. I'm basing that on my experience in attempting runs for BCM30, where I was getting down about six times per hour.
I suspect the method is impossible for NTSC and PC however. Based on a few reports, it looks like the Elite will always die before he hits the ledge. At any rate, I haven't had any report of success.
Incidentally, the method is certainly much easier than FrogBlast's 2002 Shade stop method. It's easy enough to feel routine, whereas the Shade method needed a lot of effort when I tried it. I find it kind of amusing to think that this Elite has been there all the time - nine years since FrogBlast's descent - waiting to help you down to the snow.
History and links
I got down using this method in February 2011, just after releasing my movie showing a descent via Hunter. That made him the third type of covie to help me down off the bridge by stopping me on the ledge, the first having been the gold Elite. I didn't consider him until after releasing the Hunter movie. I thought it might be difficult to get him to swipe at me suitably, but actually it turned out to be quite straightforward. On the 21st I released BCM29 which showed the checkpoint routine described above, and BCM30 in which I just got down fast. They were advertised in the HBO forum and also in the High Impact Halo forum.