Built so it could still move under it's own power when it was 1/2 it's orginal width. I wish this had shown up when I searched the web, but nothing out there about it. Wouldn't it be the coolest to look over and see how they built it?!
Watch this video (make up your own audio!) and you'll see about a dozen movie gag cars, they fall apart, lose their doors, and then there's the breakaway special at minute 7:07! The movie was titled "Highway Havoc"
Thanks to Peter in the Czech republic for finding it and sharing it!