If there's a breakdown lane on both sides, for lane closures, there could be lane shifts and utilize the breakdown lane.

@PeoriaChronicle :
Sure, if everyone is doing what they're supposed to do, it works fine.But my point is, if traffic is moving along just fine at the posted work zone speed limit, there's really zero need to wait to merge at the chokepoint.And if things are moving along just fine at 45 mph as the work zone limit starts, there's really no reason to zip along in the merge lane at 55 or 60 mph, passing several perfectly reasonable places to merge, to get to the chokepoint and bring everything to a standstill just because you can.

It only takes one [selfish] driver to ruin the zipper effect.

@CCubs : Yes, like PJ Hoerr the other day.

@CCubs : and that's its big downside, it completely ignores the human factor. When it's done right, it works like gangbusters. But getting 50 or so motorists to all work together like that with no leadership and no way of communicating is like herding cats. But I'll completely agree that zipper merge is the way to go with in-town and near-town driving. I don't think it works well with highway driving, however. The factors involved make it unrealistic in my opinion.

@AntiRanchDrssng : Exactly. That construction zone starting at Route 6 is so infuriating because the actual construction is well into 474, but they have to make Route 6 and everyone going to 74 suffer. It should really just be left lane is for 474 traffic and right lane is for all 74 traffic and no merging is needed.