Downhill Wheelchair Biking

I found this website and I thought it was really neat!  It is truly amazing at how much a person can do with a wheelchair.  This is so extreme!

This activity would be hard to facilitate without the actual company.  There are two bikes that are available to order that come in a variety of colors that you can choose from.  Other equpiment you would need would be: a standard racing helmet, protective clothing, and protective pads which all of these items would be available at a motorcross racing store.  I would say that the population for this activity would have to be people who are not only wheelchair users but at least at the mental/developmental level of a 18 year-old.  This looks pretty extreme!
The purpose of this specific website link I posted was to give wheelchair users, along with able-bodied MTB riders, the opportunity to enjoy the thrills of off-road downhill 4 wheel mountain bike riding. 

http://www.roughriderz.co.uk/downhill.html