Last year there was a parade after the World Series (MikeJ might be dealing with that this year), 800k people from the surrounding metro area packed into downtown KC. It was so bad people started ditching their cars on the shoulders and medians of I-35. We had a couple guys with routes in the area, and several more caught up in the traffic. A lot of it came back because they just couldn't get in there.
The Big 12 conference has their championship tournament in downtown KC each year (even though MO isnt in the Big 12 anymore) that's a week long mess that thankfully I don't have to deal with either. Our St Patrick's parade messes a couple guys up each year too.
Fall festivals, marathons, anything goofy I hear about that's gonna have a major affect on one of my routes I just call in or plan a vacation around it. Like 2wheeldriver said just isn't worth the headache to me. If they know it's coming they should plan better with the customers to get everything in advance, even drop a loaded trailer if the volume justifies it, because big trucks have no business delivering in a mess like that