sigh, beijing is a city full of many many people, too many people in fact. everyone you speak to says that there are, which logically could mean that they all wish to annihilate each other.
having been on the roads, i don't deny it. constant beeping and craziness, te chinese handle roads like they do queues (they don't), so as a driver in beijing you'll be a hundred times more alert than in england for swarms of bikes/people in the middle of the street/other cars/street vendors selling either melons, bottles of water or socks/blaring articulated lorries wanting to commit suicide and cut in front of you. 
it's not so great for pedestrians either, as the air makes the city even more smelly than it could possibly be. i've got a sore throat venturing outside, so i may invest in a fetching surgical face mask, at least to make me look scarier.
Bleurgh! Smokey badness, oh well... there be more to the Big City than air pollution. Good luck with your exploring