MondayâÄôs inaugural run of the new Northstar Commuter Rail line marks a new milestone for mass transit in the Twin Cities metro area. If the Northstar trains match the unqualified success of the Hiawatha light-rail line, it will be a strong mandate for continued rail development in the Twin Cities. Though expensive, public rail projects in dozens of U.S. cities have proven transformative. MinneapolisâÄô Hiawatha Line is no exception âÄî it has proven a powerful stimulus for development, has reduced single-occupant car commutes and has already surpassed ridership levels projected for 2020. There are several other mass transit projects in various stages of planning and implementation in the Twin Cities area, including more federally subsidized light and commuter rails, as well as bus rapid-transit routes. Especially attractive and relatively unknown, however, is the proposed revival of streetcars in Minneapolis. This system, which has already been designed and researched, has the full support of Mayor R.T. Rybak and lacks only funding to move forward. Modern streetcars, which tend to be far more cost-efficient than light or commuter rails (but generally rely on local funding), replace bus routes but boast higher ridership and greater community investment. In Portland, Ore., a line costing only $100 million spurred over $3.5 billion in nearby development. Ongoing investment in mass transit is a vital component of sustainable development in the modern city. If public enthusiasm continues to rise and momentum builds in the Twin Cities, state and local leaders will do well to throw their weight âÄî and their dollars âÄî behind new projects.