The Minnesota DOT website is widely cited by proponents of the zipper merge as a way of reducing congestion. However, it makes no claims about increasing throug

The Minnesota DOT website is widely cited by proponents of the zipper merge as a way of reducing congestion. However, it makes no claims about increasing throughput...it is about maximizing road space utilization. Early merges occupy more space, but the benefits to this space utilization are ancillary to the throughput congestion: fewer cross streets or exits are blocked by people not intending to use them. The question of lane change conflicts is not exactly clear...what is a conflict? When someone doesn't want to let you in? If so, that is a question of human behavior, not the physics of the situation. The Virginia site recommends late merges for when >20% of the vehicles are heavy vehicles, which is due to their merging complications (maybe something to do with those pesky "lane change conflicts"). It is obviously not a general recommendation. There is no clear data for either position on throughput...because ultimately throughput is limited by the bottleneck, which is the lane closure, not the merge behavior. People who spend too much time in their cars tend to be religious about the appropriateness of certain driving behaviors, and like any faith-based conviction, will tend to over-extrapolate empirical evidence to their context of choice.