The zipper merges is the process that the flipping DEPARTMENT OF TRANSPORTATION tells you to do. When a sign says merge ahead, wait until the merge point to change lanes. USE BOTH LANES UP UNTIL THE MERGE TO PREVENT A BACK UP!
With road construction back in full swing, it's VERY important for drivers to understand this. Use both lanes during backups, even if it says lane closed ahead. You are suppose to wait until you reach the point where the lane ends. It's called the Zipper Merge, and the effectiveness is demonstrated here...