New York Times: This city’s network of arterials, five ring roads bisected by nine more freeways, is barely two decades old, but it already is sclerotic. Roughly four million vehicles clog Beijing roads, seven times the number about 15 years ago. On any given day, another 1,500 new vehicles join the crush. So it is no surprise that Beijing has some of the worst air pollution of any big city on earth. No, the surprise is this: Beijing’s air is actually getting cleaner. China may have a …