Again, the riddle:  

Currently the top speed for this common form of mass transit is 36 km per hour.  That speed record may jump to 60 km per hour in the next couple of years.  What mode of transportation are we talking about?

Answer:  The elevator

Source: http://www.architectmagazine.com/blogs/postdetails.aspx?BlogId=mindmatterblog&PostId=107437