The contrail is a device designed by Pepin Gelardi and Teresa Herrmann to promote the development of bicycling communities. It attaches to the frame of your bike and coats the rear wheel with colored powdered chalk.

Once the contrail is in place, you will leave a colored trail everywhere you go. The idea is that as more and more cyclists use the same paths, the colored trails will thicken and brighten. You will quite literally be able to see the strength of the biking community in its rainbow trails. The contrail will also contribute to safety because drivers will constantly be reminded of the presence of cyclists. Plus, the chalk trails will provide cyclists with visual direction toward the safest routes.

Unfortunately, the contrail is still just in the conceptual phase. Read more about it at Studio Gelardi's website. I definitely want one. I like this concept even more than the pedal-powered bubble machine.