"Our experience was that the Caravans did not travel nose to tail and we saw no traffic issues. I'd guess that Caravans do bring in more rigs and people as many of them might not otherwise drive to Alaska."
I suspect that in the cold light of day, the caravans don't appreciably impact traffic, but within a few week span last summer, I had the Murphy's law experience: mid-June, leaving my buddy's house outside of Palmer (on a narrow two-lane) in the morning just as a 30+ motorhome caravan was departing the nearby "RV Park"....between the departure pattern and the slower traffic, the normal 10 minute drive to Palmer took about 45 minutes. Similarly, leaving Seward a couple of weeks later, left behind about 15 motorhomes.....unfortunately, not many passing lanes near Seward and it took until the Slodotna cut-off before I could drive my truck anywhere near the speed limit. Not the end of the world in any case, just a noticeable change.