The Baltimore Greenways Trail Network is a relatively new idea. Other projects working their way through Maryland’s transportation pipeline, including the Purple Line, the cancelled Baltimore Red Line, the Corridor Cities Transitway, and the Southern Maryland Rapid Transit Project, each date back decades. But the Baltimore Greenway, a proposed 35-mile network of urban trails ringing almost the entirety of Baltimore City, only dates back four or five years — Rails-to-Trails Conservancy’s earliest planning meetings for the project launched toward the end of 2015. But despite its newness, the trail network, spearheaded by a coalition with more than 40 stakeholder members, has a key advantage: it’s already almost done.