Found this today while watching old monster truck videos. The first 2 minutes are about arenacross featuring bike's, trikes and quads. One starting row is about 12-14 quadracers and 1 honda lined up.
http://www.youtube.com/watch?v=QX3riTLNjXg
Nice. Quads and trikes didn't really have the room they needed.
Why would anyone want to do that?
It's like a bumper car race.
Last time I raced arenacross on my dirtbike, it was pretty much the same tight, bar banging track. The kicker was the dirt worn thru to concrete in the Main. Those turns got real slick!