It is an October evening in Beijing, well past dark but the streets still crowded with rush hour traffic, and I am walking through a wide railroad underpass heading toward a Wal-Mart that I can see on the other side of the tracks. The acrid mist of polluted air turns the dim underpass lights into fluffy, yellow marshmallows. I join a single-file line of pedestrians pressed to one side, cautiously bucking a continuous stream of approaching homeward-bound cyclists, four and five abreast, none with lights or helmets and completely silent, the concentration of riding a few inches from others on all sides preventing any conversation and draining all expression from their faces. The only sound is the buzz of a thousand bicycle chains passing over cogs. The cyclists emerge quietly out of the dark, acidic fog and flow past us as relentlessly and inevitable as the future.