These are really kewl
http://www.youtube.com/watch?v=Kjw5GhyZUu0&feature=youtube_gdata_player
We have on here in NJ thats even better then that Basically its a concrete 1/4 circle shaped track that you ride down in a little open cart about the same as in the video. You can actually steer it somewhat in the track by leaning from side to side and has a single lever between your legs for a brake.
They have it at a place thats used to be called "Action Park". that also has a bunch of water rides Dont remember what its called now. but tis at one of the Ski resorts thats used for snow skiing in the winter.
Its not uncommon to see someone all scraped up all to hell because they leaned too much into a turn or for too long too fast.
Just looked it up. Its currently called Mountain Creek Water park
Anyway. dont know if they still have it or not. Its been about 10-11 years since I took my son there
But it was identical to this
http://www.youtube.com/watch?v=rDJ2hDn4IjY&feature=related