Actually, this is suboptimal.

The optimal flow is for everyone to use both lanes up until the last moment, and then to merge by alternation (one car from one lane goes, then one car from the other lane goes).

Unfortunately, this only works when a substantial majority of the drivers understand that this is how it should work. If you don't hit that threshold, then the people who use the disappearing lane are going to get glares.

Here's a link that describes the theory behind optimal merge patterns:

http://jksqr.blogspot.com/2008/09/optimal-lane-merging-part-...