Human-powered travel: Our May editor's challenge is open for submissions

Photo: Mitchell Clark Our May editor's challenge is now open for submissions. The theme this month is human-powered travel, so we're looking for photos of people moving through the world under their own power, using means of transportation mundane or exotic. Some examples: people walking, hiking, skateboarding, biking, roller-blading hand pedaling - whatever gets them places without a motor. The challenge is open to photos taken at any time. The last day for entry will be Saturday, 17th May (GMT...