@Roy Kamisato:  Where are you getting your facts that all street level rail systems require 2 lanes of traffic?  A guide that I am looking at from the American Public Transportation Administration states that most modern systems only require one lane.  The width of the largest ground level light rail cars are similar to most buses in use today (8 ft. 8 in.), so I question your facts.  Here is the document I was talking about:  http://www.apta.com/resources/standards/Documents/APTA-RT-ST-GL-001-13.pdf  There are even real pictures of a system already in use Seattle and Tacoma Washington, so a rail system taking one lane at ground level in each direction can be done.