My family joined 101,653 of our neighbors at the Minnesota State Fair on Thursday (opening day). There is a lot of construction happening, but I haven't heard much grumbling about traffic around the fair. Amazing given the large attendance at the fair.
The state fair draws 100,000 to 200,000 per day with the record attendance being set at 234,384 people on Saturday, September 4, 2010. Over the twlve days of the fair, they draw approximately 1.7 million people. To put this in perspective, Ohio State (NCAA leader in attendance) averaged about 104,000 attendees per football game. The fair does more than that every day for almost two weeks!
I've only missed going to the fair once in my 38 years on this planet. When I was a kid... traffic really was a mess at the fair. Over the last ten years, the staff at the fair have done an amazing job of working in transit and bicycling. Parking on the fair grounds can still be a challenge, but there are a lot of stress free alternatives.
We took a bus from the University of Minnesota parking lot by TCF Bank Stadium at 8:45. We waited about a minute and a half for a free coach bus to pull up. Then we had a comfortable five minute ride on the dedicated transitway to the fair. The return trip at 2:30 in the afternoon was equally efficient (and the air conditioning was greatly appreciated).
If you go to the fair, the U of MN park and ride lot is a slick way to go since it has a dedicated transitway.
If you ever work on a traffic management plan for a large event, check out the state fair's website to see how they've integrated transit. They're a great case study. And as long as you don't call them in August, I've heard the fair staff are very happy to talk to folks about their system.