This museum is close to the east side of Qianmen Subway Statiion, southeast corner of Tiananmen Square, east side of the old Beijing Railway Station. The admission fee is 30RMB, pay extra money for the multimedia shows. It is close on Monday. In fact, I haven't been there before. If you are interested, see it after you see the Tiananmen Square.

Thank you for the directions. It was very easy to find (it's just behind the railway museum - you can use the underground tunnel to cross the street). This place is definitely worth the trip; it has tons of minatures and they have these cute videos of transportations in different eras. I would set aside about 2 hours to see it. The multimedia show was kind of interesting too (only 10 RMB). It talks about the future plans for Beijing transportation.