To visit Bogotá, Colombia on a Sunday is to witness an unforgettable spectacle: miles and miles of car-free streets packed with cyclists, runners, and walkers. This summer, I walked from my hotel down a hill to Carrera Séptima, a wide avenue where men on Italian road bikes zoomed past teenagers on mountain bikes they’d outgrown. Grannies on rusted cruisers glided alongside dog walkers. Together, they formed a torrent broken only when a few people periodically…