from an article in Good
Brooklyn-based designers Pepin Gelardi and Teresa Herrmann have designed a “Contrail,” a receptacle filled with a colorful chalk-like fluid that turns bikes into paintbrushes.
The idea came out of the designers’ wish for a way to show the biking community just how large of a community it is by visualizing the many crossing paths that cyclists take throughout cities.
See more @ the web site BikeContrail.com where it is billed as a “bicycle advocacy tool”