Caltrain is developing a new business plan this year, and one group is asking the agency to consider adopting affordable housing development as a priority for its excess land along the rail line. That way, people can live in greater density without adding to the region's car-driven traffic problems.

The Housing Leadership Council of San Mateo County is asking the transit agency to consider adopting a "transit-oriented development" policy, according to said Leora Tanjuatco, the leadership council's organizing director.

Such a policy would formalize the agency's priority of building homes on its land, she said. A key part of the group's request is that the policy include a provision that at least 20 percent of any housing permitted on Caltrain land be designated as affordable.

Caltrain owns over 30 acres of property scattered throughout San Mateo County, mainly in the form of spacious parking lots, that could be rearranged to allow for high-density housing. The territory comprises "parcels of land that have been hiding in plain sight for years," Ms. Tanjuatco said.

In Almanac territory, she said, the agency has about a half-acre in Atherton and two acres in Menlo Park.