Contrary to one of the recommendations in the article, the Minnesota Department of Transportation recommends against merging early, and instead has made a large public-education effort (including signs at merge points) to encourage zipper merging:
Zipper merging works far better in practice than the early merging proposed in the article. To begin with you usually can't see where the land ends well enough to merge early, and once things slow down you're screwed. Zipper merging works great if everyone expects everyone else to do it. The problem in the US is that people trying to zipper merge are punished by drivers who think early merging is polite.
Most drivers (at least in Australia) will be courteous in this way. Where it breaks down is that the point of merging tends to move backwards, eventually to a point where drivers are merging quite early, sometimes to the point where arriving vehicles don't even know a merge is occuring. What then happens is drivers push ahead and attempt to start a new merge close to the barrier/traffic cones again. However no one wants to merge twice and see these restarts as skipping the line.
The OPs main point of leaving larger gaps might solve this, but generally gaps will fill and you are then back to gridlock.
This accords with my own experience driving in Sydney, where the need to merge is frequent, but not Canberra, which has more more US-like freeway system.
Brisbane had a few bad years of building insane combined on/off ramps that tend to block frequently as everyone needs to be in that lane but with three or four lanes of traffic. Hale Street as you pass Suncorp Stadium is a particularly bad one.
Their research is fundamentally flawed...and it is rooted in an fruitless desire to optimize something that is physically unoptimizable. There is no sand-arranging possibility that can cause the falling-rate of sand in an hourglass to change significantly.
Merging later encourages better utilization of road capacity and eliminates bottlenecks further away from the overloaded resource. It's quite simple really, in this case the polite behavior is wrong, and if everyone would just be greedy, the behavior would no longer be impolite and would be more optimal (source, I live in china, this really works better than the alternative, we have plenty of overloaded resources).
Every advocate always has their pet theory as to why their method works better than others. They also have "evidence" which is either completely anecdotal or does not control for even the most obvious of factors (such as rate of queue arrival or average speed in the constrained resource).
Simply put, they are all wrong. A bottleneck is a bottleneck and there is no fairy dust magic queueing technique that works better than another. At best, some techniques might have a behavioral advantage...but I stress again, they are all inconsequential. We are talking tens of seconds of time savings at best.
Bandwidth is probably the wrong term here. It keeps traffic from backing up as far, true, but this really only matters to people who are turning off before the merge.
Ignoring early exits, at steady state, the only thing that really matters is flow _after_ the merge - that's what determines the rate at which traffic passes the restriction.
I would never try this myself mind you; I hate pissing people off in the road in the states and I'm happy to outsource my driving to a taxi driver in china.
However, it's a simple matter of utilization, if everyone waited properly in line, traffic would seize up in Beijing as many intersections would become blocked by single lines of cars next to empty unused lanes.
We are talking about saving minutes, 10s of minutes, or even days [1]. Funny how Americans haven't seen real traffic before and think they know the right global solutions.
Assuming this is true, zipper merge is still a vastly preferable system.
1) It's a more effective use of the roadway. Why have 1 lane of traffic backed up for 2 miles when you can have 2 lanes of traffic backed up for 1 mile?
2) It's equitable. Everyone moves at the same speed, there's no way to game the system for personal advantage.
It's not evident that this is a more effective use of roadway, as the article hints at.
The problem is the bottleneck point, where people are obligated to move into one lane. This is what causes delay - the faster you can get cars moving through the bottleneck point, the less delays there will be behind. So it doesn't matter so much where the cars behind are positioned to wait.
Zipper merge likely causes more delay - in practice - as there has to be a late negotiation over whose 'turn' it is to merge. If this negotiation is planned earlier, it doesn't need to have such an effect (in fact, I imagine it could eliminate all the delay) at the bottleneck point.
I think the point of zipper merging is that the negotiation has, in fact, been planned a couple miles before the actual merge point, so that the cars are alternating like
Minnesota DOT probably recommends zipper merging because they are taking into account that it's likely a safer (and easier) method for drivers in denser traffic.
That might be true, but it certainly sounds like a behavioral, not absolute, position. If it is behavioral, you have no guarantee that what works in Minnesota will work in Illinois, let alone a different country.
http://www.dot.state.mn.us/zippermerge/
More discussion:
http://www.drmomentum.com/aces/archives/003800.html