The Death and Life of Great American Cities was published in 1961. It’s understandable that back then, urban planners thought single-use zoning was great. Cozy residential neighborhoods, grand shopping districts, polluting industry far away, beautiful soaring towers with verdant parkland in between - who wouldn’t be seducded by that vision, standing in contrast to the craped and crowded hodgepodge of tenements and dingy streets of most cities at the time?

But Jacobs started a revolution in the way we think about cities. Now we know that mixing uses creates a more vibrant urban fabric and a safer environment because of “eyes on the street”. We’ve learned that building to human scale, such as storefronts right on the streets rather than interposing large parking lots, or small jazz cafes rather than huge sports stadiums, fosters a more vibrant and creative population. And it’s been well established that communities thrive when they have abundant public spaces for people to congregate formally and informally.

Yet elected leaders continue to propose or support projects that rend rather than knit the urban fabric. At the Rhode Island Red Line stop in Washington DC, the Metro wants to replace a large parking lot with a smaller garage, encouraging a more mixed-use, pedestrian-oriented neighborhood. Unfortunately, some neighborhood activists don’t understand the many things we’ve learned since Le Corbusier and Robert Moses, and continue to push for destructive development policies even if their hearts are in the right place.

As an architect recently pointed out to me, no matter how much professionals in the field may have learned (though many still haven’t), in a project the client calls the shots. And as George Santayana famously said, those who do not learn from history are doomed to repeat it.

David Alpert is Founder and President of Greater Greater Washington and Executive Director of DC Sustainable Transportation (DCST). He worked as a Product Manager for Google for six years and has lived in the Boston, San Francisco, and New York metro areas in addition to Washington, DC. He lives with his wife and two children in Dupont Circle. Unless otherwise noted, opinions in his GGWash posts are his and not the official views of GGWash or DCST.