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Comment by kelnos | Hacker News Reader

I've rarely seen people in (northern) California do proper zipper merges. CA has some of the most clueless and inattentive driving I've ever seen.

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I rarely have seen issues in California with zipper merge, when the lanes are actually merging. Most of the time the issue I've seen is when people are cutting over from a turn only lane to try and force their way to go straight.

Yeah, that situation is where I see it 2nd-most; first most is people trying to change lanes into an exit lane right at the exit when they're in a non-exit lane and want to exit. Those are lane changes, though, not merges.

Turn-only lanes (using a turn-only lane to go straight) is where I see the worst cheater/vigilante behavior. (It's always BMW's who do it, too... )

Those turn-only lanes are just wasted capacity that could be used to carry more traffic into a zipper merge. I'm guessing that at some peak hour the turn lane has utility, but at reverse-peak they should be able to switch to a regular lane leading to a merge point.

Zipper merging inside an intersection will almost certainly lead to gridlock due to incomplete mergers before the light changes.

Referring to exit-only lanes on highways, not signaled intersections.

Disagree. I used to reverse-commute through the Golden Gate Bridge and the Caldecott Tunnel, where the freeway went from 4 lanes to 2 in both places. 99% of drivers manage to zipper-merge properly. Likewise, almost everyone zippers at the South 101 Central Freeway merge.

California drivers may or may not be bad, but they're much better than the ones in Minnesota.

I wish some of the "exit only" lanes would change to be zipper-merge-able-- in SF, think about the 7th street exit on 80E just before the Bay Bridge-- two empty lanes!-- and lots of "cheaters" whereas with a zipper merge everything would move faster.

IIRC California officially endorses early merging, though?

You could just make two exit lanes in that case, and merge them as or after they exit. People exiting at the last minute from a non-exit lane though aren't really merging, but rather changing lanes. And it doesn't really result in a proper zipper merge since not everyone is exiting, so you can't predictably alternate cars.

I guess I mean that they shouldn't be exit lanes at all, but should be used as extra capacity to facilitate zipper merges. In the case above, the exit lanes stretch back almost 1/2 a mile, which is waaay above the actual demand for that exit, esp in the evening hours.

Oops, I read your case backwards (I'm not familiar with that exit). I thought you meant that there were too many people exiting for the one exit lane, so you were proposing people from the 2nd-to-right lane should be able to zipper-merge into the exit lane right before it exits.

The reverse (merging out of the exit-only lane to stay on the freeway), I think usually works better with a late-merge, but you do still have the problem that you can't do a proper zipper merge, because the lanes aren't fully merging, so you can't alternate one-right/one-left. Instead some cars want to lane-change and some want to continue in the lane, which adds at least a little complexity.

It could be partly improved by signage changes though, it sounds like, to just mark the exit lane later.

I still commute occasionally across the bridge. Getting people to zipper merge 4 to 2 lanes properly going onto the bridge almost never happens.

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