Editor’s Note: Eric Kober is an adjunct fellow at the Manhattan Institute. He retired in 2017 as director of housing, economic and infrastructure planning at the New York City Department of City Planning. The opinions expressed in this commentary are his own.

Local control of land use and zoning regulations has created two models of growth in America’s metropolitan centers: expensive cities and expansive cities. And both models are leaving low- and middle-income workers behind when it comes to affordable and convenient housing.

Expensive cities, like New York, San Francisco and Boston, are geographically constrained by coastlines, bodies of water and other natural barriers. As they grow, property values rise and housing supply fails to keep up with demand. Expansive cities, like Atlanta, Raleigh and Austin, do not face geographic obstacles to growth so they continue to expand by enlarging the outer boundaries of their metropolitan areas.

Higher-skilled, better-paid workers are almost always able to find housing options that work for them no matter which type of city they reside in. But what about the low- and middle-skilled service workers metropolitan areas rely on to staff local government, health care, education, childcare, retail and restaurants? In expensive cities, those workers have limited affordable housing options and are often forced to live far away from employment, requiring long, arduous and expensive commutes; while in expansive cities, some workers may find affordable housing near their jobs, but may have to suffer through traffic or long commutes. In these areas, everything is so spread out it’s difficult to put public transit in place.

In both cases, cities need to provide more housing options for low- and middle- skilled workers that is affordable, close to jobs and accessible to public transit. Housing affordability issues are particularly dire for households with incomes below 40% of the national median and for those who live in expensive cities. But even in relatively affordable, spread-out cities, time spent commuting in traffic decreases quality of life.

The practice of zoning most residential land exclusively for single-family detached homes is a major cause of affordable housing shortages and long commute times. In expensive cities, this policy makes it impossible for housing supply to respond effectively to shortages. Single-family zoning creates nice neighborhoods for those who can afford them. But it often excludes many others. In fact, the origins of single-family zoning lie in efforts to keep people from buying homes based on their race or socioeconomic standing.

Today, single-family zoning serves to prop up home prices and give incumbent households a reason to oppose new, denser housing that might lower prices of existing homes while bringing more families with children into the community, causing school taxes to rise. This only perpetuates the wide geographic spread between the service jobs that are available in affluent communities and the housing where the workers who fill those jobs can afford to live. In expansive cities, it encourages new housing to be built far from existing jobs. In both, it encourages an environmentally unsound, car-dependent lifestyle.

In the past decade, the primacy of single-family zoning has been challenged. States and cities that recognize the problems with it are experimenting with innovative solutions that increase housing unit density and give households more choices closer to where jobs are. These include accessory dwelling units (converting garages or basements to apartments), legalizing small multifamily buildings (2, 3 or 4 units) where single-family homes are permitted and allowing larger apartment buildings along transit corridors and close to job centers.

For example, Minneapolis now allows duplexes and triplexes on what were formerly single-family-only lots. Oregon allows duplexes, triplexes, fourplexes and “cottage clusters” on formerly single-family lots in cities with populations over 25,000. In cities with populations of more than 10,000, duplexes are allowed. California permits a detached second home on formerly single-family lots and the conversion of a portion of an existing home to a third unit.

These solutions can shorten commutes while making housing more affordable in the high-opportunity places where many people want to live. More cities and state legislatures should follow the lead of these forward-looking measures. To be sure, no property owner is forced to add a second unit; most homes will remain as they are. But these measures create an economic incentive to add housing where it’s most in demand.

These are not panaceas, however; expensive cities need to expand vertically as well, but allowing more apartment buildings, even near transit and jobs, has proven contentious. However, the recent attention to urban density restrictions and impediments to affordability and economic growth suggests there may be progress in state and local housing battles in the near future.