The kicker for us will be if they use the highway (or I guess the one other highway) to get here from Boston, NY, or MTL. We have exits that back up on a busy Tuesday afternoon around here! The state highway in front of my office backs up a half mile most weekdays at quitting time.
And, we have roads to trailheads closed down especially for the eclipse to cut down on damage to muddy trails, ski areas controlling access or going pay-per-view, city streets closed in town, "notch" roads that your GPS will tell you to use but are closed for winter still- and lots of "can't get there from here" places where one truck getting stuck trying to turn around means a 40-mile detour!
I really hope it isn't chaos, I hope it's fine, but I personally won't be anywhere in a car anytime 3 hours either side of totality if I can help it.