Look out, Laurelhurst: Dense housing is coming if the leadership of the Oregon Legislature has its way.

In December, House Speaker Tina Kotek (D-Portland) proposed to make Oregon the first state to do away with single-family zoning and allow up to four units on properties currently zoned for single-family housing.

This week, Senate President Peter Courtney (D-Salem) proposed to outdo that bill by requiring cities to allow even greater density around transit.

Senate Bill 10 would require metro-area cities to allow 75 housing units per acre within a quarter mile of frequent transit and 45 units within a half mile. That number goes up to 140 units within a quarter mile of a light-rail station.

Under current zoning in many single-family neighborhoods, like Laurelhurst, there is often no more than one house per 5,000 square feet of land. That means eight or nine units an acre—or up to 18 units if you include backyard cottages and other accessory dwelling units.

The Courtney bill focuses on areas where there has been public investment in transit. Backers of more transit and more housing say it's just the beginning.

"Portland has done a great job of building a better transit system than most cities, but we're not going to get to the next level of transit use without significant growth in housing near those lines," says Michael Andersen of Sightline Institute, a sustainability think tank. "The only thing we need to do is get out of the way."

The map above shows locations in Portland within a quarter mile and a half mile of frequent transit, according to TriMet.