In this fawning article, entitled "Four Bike Heroes", Larry Gallagher stumbles on a very good reason to bike or walk through San Francisco: In this stretch, one stands an extremely good chance of inadvertently witnessing someone either injecting something into or extruding something from his or her body. In a car, one is exposed merely to the constructed problems of congestion, freeways, and toll plazas (cf. the Examiner's current series on traffic).