Research shows the zipper — which is a late merge, using both lanes as long as possible, not moving over right away — is often safer and will keep traffic flowing. The problem is, among your fellow drivers, it’s not the most popular move. Traffic engineers recommend the zipper merge not just on super highways, but also on roads like Route 9 in Massachusetts. The zipper merge is legal, but there’s no universal campaign to educate drivers.
https://www.wnpr.org/post/zipper-merge-may-seem-aggressive-its-actually-highway-congestion-reliever