"Regional transit coordination provides the best transit experience in an urban area. It enables better, more affordable transit which in turn improves ridership. After 50 years of experience in Europe, the U.S. should finally embrace the concept."

https://www.planetizen.com/blogs/127695-transit-coordination-leads-better-transit-and-more-riders

With links to Mineta Transportation Institute (MTI) research reports.

"In sum, whether one agency or 27, public transit within a single metropolitan area must be coordinated in a seamless, effective, and efficient way, which will attract riders and ensure its survival in this post-pandemic world. We call on the US Federal Transit Administration (FTA) and the State of California to recognize the value and importance of such agencies. Maybe then our metropolitan areas will begin the process of metropolitan areawide transit coordination as most European areas have done. This may be achieved through a German-style verkehrsverbund or Swedish-style full consolidation; however, in either case, the transit riders—as well as the livability—in our metropolitan areas win."

And for the seriously interested we have:

https://www.worldtransportjournal.org/journal