Students of how cities have been built throughout history know that transportation drives development. The transportation systems a society chooses dictate the form of their cities.

Area civic leaders recognized that dictum when they built the freeways in the 1960s, radiating from the District to surrounding counties. This allowed the postwar growth of Arlington, Fairfax, Montgomery and Prince George’s counties. Smart planners then recognized that building laterals to connect the radial freeways in the suburbs, resulting in the Beltway, would spur suburb-to-suburb economic growth.

Showing remarkable foresight, the civic leaders of this region invested in the first new heavy-rail system the country had seen in decades. Starting in the late 1970s, Metrorail radiated from downtown D.C. in a manner similar to the freeways. Today, more than 80 percent of new employment growth occurs within walking distance of a Metrorail station, providing employers and residents an environmentally sustainable way of living and creating wealth for their families and the region.

Streetcars in Arlington County and the District as well as Maryland’s proposed Purple Line light rail are the next steps in this evolution.

Just like the Beltway, the Purple Line will laterally link the Metrorail radials to connect growing, walkable urban places such as Bethesda, Silver Spring and New Carrollton. Eventually the Purple Line should circle the District as the Beltway does, linking suburbs to suburbs and generating continued economic growth.

Streetcars will also link the Metrorail radial lines within the District, allowing Anacostia, Capitol Riverfront, H Street, NoMa, Shaw and Georgetown to be linked. The Columbia Pike streetcar in Arlington will create a high-density walkable urban corridor from the Pentagon City Metrorail station to Skyline. This will bring the forlorn Skyline area into the economic mainstream.

The revitalization of Columbia Pike will increase the quality of life of the surrounding single-family neighborhoods, as has happened around Clarendon and Bethesda. These neighborhoods will have the best of two worlds: suburban splendor within walking distance of restaurants, groceries and rail transit.

Modern streetcars in this country have a proven track record. There have been outstanding success stories. Portland, Ore., and Seattle stand out. Portland’s first-phase streetcar line cost about $100 million to build but resulted in more than $3.5 billion in private investment in a decade. The first modern streetcar in Seattle, going from downtown to an obsolete industrial area to the north, in a mere decade has resulted in Amazon moving its corporate headquarters there, a biotech cluster anchored by the University of Washington Medical School and thousands of new residences.

Streetcars have shown that the corridors they traverse redevelop rapidly, which did not happen with buses. Why? Streetcar lines are permanent, signaling to the private market that the transportation system is not going to change tomorrow. Also, middle-class Americans like streetcars. Consumers who have a choice ride streetcars and other rail transit but generally not buses.

I have seen billions in privately funded economic development around streetcar, light rail and Metrorail stations. I have yet to see much private investment at bus stops.

Of course, it takes civic will and leadership with the intention to create great walkable urban places to take advantage of the transit investment. Thirty years ago, Arlington, the District and Montgomery County showed that they have that intention and required planning skills. They also have a commitment to transit-accessible affordable housing, though much more is needed. Prince George’s now is planning for transit-oriented development. Even far-flung Fairfax and Loudoun counties have taxed themselves to extend Metrorail service.

Opposing streetcars and light rail today would be like opposing the building of freeways, the Beltway and Metrorail in the 20th century. Along with maintaining our roads and Metrorail, the most important transportation investment for our region in the early 21st century is streetcar and light rail.

The writer is the Charles Bendit distinguished scholar and research professor of urban real estate at George Washington University’s School of Business and president of LOCUS (a project of Smart Growth America).