From downtown Los Angeles to Santa Monica, train commuters on the Expo Line journey from asphalt to ocean through some of the most expensive real estate in the United States. Each train pulls into stations of low-slung buildings that soon fade into vast expanses of single-family homes. The view from Los Angeles is hardly unique. Commuters from San Diego to the Bay Area and Sacramento see low-rise suburbs as the norm. And everything costs a fortune.

That might begin to change if the state legislature passes a bill addressing local land-use regulations. Introduced by Scott Wiener, a Harvard-educated attorney and state senator, SB 827 would effectively abolish zoning restrictions in Wiener’s district of San Francisco and for significant portions of the state’s most populous areas—and likely produce a boom in new housing construction. SB 827 sweeps away many local limits on height, density, and design within a half-mile of a train station—such as for BART or CalTrain—and within a quarter-mile of stops on high-frequency bus routes. So-called transit-rich zones would see local height limits lifted to anywhere from 45 feet to 85 feet—roughly from four to eight stories—depending on factors such as street width and station proximity. Cities could build taller, but they could not require that buildings be shorter. New projects built near transit hubs would also be exempted from minimum parking requirements. And as long as a particular project is up to code, no municipality could introduce design standards preventing developers from including the maximum number of units possible in a building.

Wiener hopes to fight sprawl by allowing Californians more opportunities to live closer to public transit, and to address climate concerns by reducing their need to drive. To Wiener, a liberal Democrat, housing is also about social justice. He believes progressives have “lost their way on housing,” as he told Forbes recently. Young people, the poor, and the elderly are demanding shelter only to find its supply limited by stringent regulations. “Gentrification is fueled by a lack of housing,” Wiener argues. “When there isn’t enough housing and rents skyrocket, landlords have an economic incentive to push out long-term renters by raising the rent or evicting them.”

Nearly a third of households in California’s metro areas can’t afford rent, according to the McKinsey Global Institute. A majority of these rent-squeezed households—some 3.7 million—are in Los Angeles and the Bay Area. In San Francisco and Oakland, even making $90,000 a year barely puts one above the affordability threshold. California’s affordability crisis is rooted in a housing crisis: not nearly enough homes are being built to keep up with demand. “We under-produce by about 100,000 housing units every year, and we have a housing…