Here's a link to a photo of a good old Airstream trailer.
http://www.flickr.com/photos/jackjon...7602790081263/
Notice how the top and ends are rounded? Maybe that's why Airstream trailers are the only ones left after a hurricane or tornado rips through a trailer park.
And here's more about the BMW C1:
http://www.carenthusiast.co.uk/shows/bmw_3.htm