Remember the Darknights Nationals? At the time it was THE biggest modified car show in Canada, taking place at the Markham Fairgrounds.
Competitors would come from all over North America to attend the two-day event. Most of the show participants would actually park their cars the show on the Saturday, leave to back to their homes or hotels on Saturday night and then return for the second day on Sunday. Outdoor events longer than one day can get complicated like that but they pulled it off well.
Darknights was held from 1999-2006 and was a real pioneer for shows in Canada. You can read some background info on the show here: http://www.apexmediagroup.ca/dkn-casestudy.html
Here are some photos of the 2001 event.