SAN DIEGO - Regional leaders Friday adopted a $57 billion blueprint for San Diego County highway, rail and bus line improvements, despite an 11th-hour objection by the attorney general asserting that the blueprint fails to address global warming.

The San Diego Association of Governments board voted 16-2 to give final approval for a regional transportation plan that promises to expand the freeway system by 38 percent in total lane miles between now and 2030, widening Interstates 5 and 15, and Highways 76, 78 and 56 in North County.

It also would deliver long-desired ramps connecting I-5 and Highway 78.

The plan promises to extend San Diego's Trolley light-rail system north to University Towne Center, while launching a foray into a system of fast buses built on the backbone of exclusive freeway lanes and special treatment on city streets.

One such street would be El Camino Real through coastal North County, where traffic signals would give buses a head start on cars when lights turn green.

But the state's attorney general, Jerry Brown, charged Thursday in a letter that the plan is not nearly green enough to comply with the state's new climate change laws, which aim to reduce the greenhouse gas emissions believed to be causing global warming.

Deputy Attorney General Sandra Goldberg said that the blueprint will result in a sharp increase in car travel and a corresponding increase in greenhouse gases such as carbon dioxide being emitted locally.

Association officials conceded that emissions kicked up by San Diego County's transportation system will grow by about one-third under the plan. But they said their analysis shows that an alternative plan that pours billions more into trains and buses would actually increase emissions by slightly more between now and 2030.

Goldberg took issue with that conclusion, saying the association's environmental report prepared for the plan gave no explanation for it.

But the agency stood by that conclusion Friday.

"Our research found that, given our existing land-use patterns, a transit-oriented alternative would not reduce greenhouse gas emissions because there's not enough money … to add the transit capacity it would take to serve every person in every cul-de-sac," said spokeswoman Colleen Windsor, by e-mail. "Even if we shifted as much money as possible to transit, you would still end up with traffic congestion and some auto trips that would emit more pollution."

Gary Gallegos, the association's executive director, said the late arrival of the attorney general's letter - nearly two months after the public comment period for the environmental document closed - caught everyone by surprise.

Gallegos said he spoke with Brown by phone late Thursday and offered to sit down later to discuss whether the plan should be amended to try to trim greenhouse gas emissions.

"The attorney general seemed agreeable to that," he said.

Board member Jerome Stocks of Encinitas suggested that Brown be invited to the board's annual January retreat in Borrego Springs to talk about the role transportation plans should pay in combating global warming. This plan is the first in San Diego County to even discuss global warming. Such plans are updated every four years.

While Gallegos reassured board members, some expressed concern about the implications of the letter.

One member reminded colleagues that the attorney general sued San Bernardino County last spring, alleging that county's general plan did not comply with the state's new climate change laws. The suit has since been settled.

"This is a good wake-up call," said San Diego Councilman Jim Madaffer, saying cities and the county government should be prepared to be challenged if general plan revisions don't address greenhouse gases.

"This is potentially a legal issue for us," added board member and Oceanside Mayor Jim Wood. "I'm still concerned that there is an AG letter floating around out there that someone could use to launch a legal challenge to the plan."

As for the plan itself, it in large part calls for much more of what is being built now on I-15 between Rancho Penasquitos and Escondido - special lanes that cater to a combination of buses, car pools and solo commuters willing to pay a toll. Such lanes are planned for I-5 between Del Mar and Oceanside and Interstate 805 in San Diego.

In addition, toll lanes - like those in the middle of Highway 91 in Orange County - are to be built in the medians of Interstates 5 between Oceanside and San Clemente and 15 between Escondido and Temecula.

Ron Roberts, chairman of the San Diego County Board of Supervisors, expressed concern about the emerging emphasis on toll lanes.

"We're gravitating toward a system where people who can pay will roll along on the freeways and people who can't will sit and wait," Roberts said.

But, he said, no plan is perfect and this one was worth supporting.

Not so, said Solana Beach Mayor Lesa Heebner and Del Mar Councilwoman Crystal Crawford, in casting the lone dissenting votes. They said the plan does not commit enough funds to building a robust public transit system.

Duncan McFetridge, chairman of the conservation group Save Our Forest and Ranchlands, suggested that the plan's lack of transit emphasis threatens not only global warming, but also the county's $160 billion economy. He also asserted that the plan would pave the way for development of natural treasures such as the Guejito Ranch east of Escondido.

"Roads bring land to the marketplace," McFetridge said.

Those comments prompted board member and Poway Mayor Mickey Cafagna to make clear what the $57 billion would go for.

"We aren't building any new roads," Cafagna said. "What we are doing today is expanding our existing roads to their maximum capacity."

But as far as former state Sen. James Mills, D-San Diego, was concerned, increasing road capacity was nothing short of a blueprint for boosting San Diego County's population from 3 million to 4 million by 2030.

"This will make San Diego another Los Angeles," Mills told the board. "I don't know anyone who wants another million residents in San Diego County." Three decades ago, Mills authored legislation that created the Trolley system.

Board member Ron Morrison, National City's mayor, said forecasts indicate 1 million new residents are coming whether the region builds roads or not - and that 60 percent of them will be children born to San Diego County families.

Near the conclusion of a two-hour discussion, Supervisor Bill Horn quipped: "Unless we are going to castrate everybody at 10 years of age, we might as well as support this plan."

Contact staff writer Dave Downey at (760) 745-6611, Ext. 2623, or ddowney@nctimes.com.