Xtracycle makes a brilliant load carrying system for regular bicycles. A travois is a Native American conveyance in which 2 poles are yoked to a horse or dog, with cargo and passengers sitting upon a platform between them: a dragged A-frame. Xtravois is inspired by both. It's the family car.
There's a video clip (6.2MB) available commemorating a bright spot of the highly technical design process. The De Cecco pasta girl nearly made it onto the headtube.
I designed Xtravois as a done-right successor to this hack (seen in the first photo), which blew up after about 5K miles. I went on to develop the electric assist component into a product for nearly any regular Xtracycle.
Many people ask if I am selling frames like this, or if I have build-ready plans available. No. If you are serious about having your own, I'm happy to offer tips on details not apparent in these photos, things I'd do differently now, etc. But you're on your own as far as actually building it. -- Todd Fahrner