I take it the merc driver can't read or understand the signage, or is he sooooo important that he has to be at the front of the Q. The reason the traffic is at a crawl is because of people like him , if everyone filtered in 2 or 300 yards further back a sensible speed would be maintained , those who think that the 100yrd signs just there for show cause the problem. Do it now ! Your a long time dead !!

I think that's counter to current thinking that the late merge (or zipper merge) is more efficient

e.g. http://www.dot.state.mn.us/zippermerge/ FL2 2011 SD4 XS in Galway Green

That zip & merge is nearly as stupid as the SNP manifesto . If someone is doing 70 on the lane that's open and someone doing 50 on the lane that's closing there is only going to be one result .. Heavy braking which constatinas further and further back . Read the sign move in advance , even if everyone is doing 40 , it's better than coming to a complete halt as what happened in the video. Do it now ! Your a long time dead !!

But surely in your example, whether they merge early or late, the 50mph car has to join traffic at 70mph? Just at a different point.

More generally, I think what you describe is an edge case. The situation in the video was slow moving traffic which (IMO) is where problems with merging normally occur.

Evidence from two studies* (where they control merge points and compare to previous measurements) suggests if the cars had spread out across the lanes and merged late there likely would have been reductions in delays, queue length and subsequently fuel consumption.

Plus, of course, the situation that started this discussion would have been avoided...

* http://trb.metapress.com/content/b471585v70138006/fulltext.pdf and http://trid.trb.org/view.aspx?id=718758 FL2 2011 SD4 XS in Galway Green

Disagree yanwoo, if someone goes to the end of the lane that's stoping there's only ever going to be one outcome irrespective of speed , it wil stop both lanes at some point thus a tailback that will never go away . The more people that leave it to the last 20yrds will get greater thus the tailback will get longer IMO.
My example re 70 to 50 for 200 or 300 yards must be better than going from 50 to zero as the traffic will stop, we have all seen it happen. Do it now ! Your a long time dead !!

I understand your logic and theory, but when they've tested it in real world contexts the results are zipper or late merge are more effective by the measures they selected. It's used pervasively in Belgium, Germany and Austria (mandated by law I believe)...which suggests it's unlikely to have the terrible issues you describe.

Here's a video from Minnesota comparing their results for one location (related to the first link I posted):

Although you're not alone in your view...they're are others whose anecdotal evidence suggests they don't work as well as the research suggests. Here's someone who experienced it as a success in Germany but not working in the US: http://www.atomicalex.com/?p=1308 FL2 2011 SD4 XS in Galway Green