New transportation projects require two things to be successful and that is what supplies the transportation project and what demands it.  For example residents in a community agree to pay an additional tax to have a new train line service them.  The people’s taxes are the supply (or money) for the project as well as the people demand additional train service to their growing community.  This is obviously a simple example for a complex relationship.  Unfortunately politics is heavily integrated within any transportation project and sometimes we cannot retrieve both supply and demand.  For example, the Hudson River crossings between New York City and New Jersey are at over capacity.  There is a clear demand for additional crossings, but there is not supply driving such projects because it is almost political suicide.  No politician will ever support another crossing because no one wants to spend the money or take away land from citizens for the right of way.