SAN DIEGO -- County voters have approved Proposition A, the measure to extend a countywide sales tax by 40 years to pay for transportation projects, according to unofficial election results from the county registar of voters posted Friday.

With more than a million votes tallied, the measure, which will extend the half-penny tax, known as TransNet, passed with 67 percent of the vote.

The measure edged past the 66.7 percent needed to pass by just 3,400 votes.

That number stood in stark contrast to the number of county residents who approved the original TransNet measure. In 1987, just 53 percent of voters said yes to TransNet.

The measure's fate had been locked in one of the tightest races in the county, but by Friday officials were breathing easier as the count wound down.

"We've gone through a lot of ups and downs and backups through the last weeks," said Craig Scott, the association's manager of transportation finance, addressing the board at its regular monthly meeting. The association is the region's transportation planning agency, which backed the extension.

On Friday, just hours before the final tally was announced, elected officials at the San Diego Association of Governments board meeting were downright giddy about the chances of Prop. A's passage and what it would mean to the region's transportation future.

There were all the trappings of a victory celebration; the thank-yous, conciliatory gestures, everything but an acceptance speech.

Many elected officials see the tax as the backbone of the region's transportation system and say it's a crucial tool in levying state and federal transportation money. Opponents had questioned whether the division of revenue in thirds shortchanged roads or public transportation.

The TransNet extension is expected to generate some $14 billion in 40 years, starting in 2008. The money will be split in rough thirds among highway and freeway improvements, local road projects and public transportation systems.

On Friday morning, Solana Beach Mayor Joe Kellejian was all smiles and thanked a long list of people and organizations for their support, including environmental groups, a number of elected officials, the building industry and the business community. Kellejian, who is chairman of the board's transportation committee, said it was time to reach out to opponents of the measure.

"Now the hard work begins and let's move forward," he said.

Poway Mayor Mickey Cafagna, chairman of the SANDAG board, echoed Kellejian's sentiments.

"We made a tremendous promise to this community," Cafagna said. "Now we have a tremendous responsibility."

Other board members spoke of the need for cooperation and extended the olive branch to county Supervisor Dianne Jacob, a critic of the plan. They also thanked her for her grit and the changes for which she pushed. For instance, she was the reason the board made the extension 40 years -- not 30, as originally proposed.

"It's a better measure for it," said San Diego Councilman Jim Madaffer.

Jacob, who represents the county's Board of Supervisors on the association board, opposed the tax extension along with Supervisors Bill Horn and Pam Slater-Price. All represent parts of North County, and Jacob's district is largely in East County.

The three said at least 50 percent of the revenue from the tax should be directed to highways and freeways. Most people wouldn't benefit from having a third of the revenues go to mass transportation projects, they said.

Critics also opposed a provision that will allow the board to change or delete, with a few exceptions, any project in the TransNet plan with a two-thirds vote of the board saying voters should be guaranteed that the projects they voted for would get done.

One project that can't be touched by a two-thirds board vote is the long-awaited completion of the widening of Highway 76 to Interstate 15. The project was promised in the first TransNet measure, but escalating costs and environmental roadblocks kept it from becoming a reality.

Jacob told the board Friday that she had long supported an extension of TransNet, but had concerns about the measure on November's ballot.

"The voters have spoken. It's time to work together. It's time to move on," she said. "There's a heavy burden for all of us to make sure the will of the voters is carried out."

Reached after the meeting and before the final tally, opponent Carolyn Chase said she expected the measure to pass. Chase, the spokeswoman for Taxpayers for Better Transportation Planning and a member of the Sierra Club, said there was no reason to celebrate.

"What's sad is that it's just a fact that there's not going to be traffic relief," she said.

She said the status quo would continue and the region would be worse for it. Chase had said that public transportation should be improved to serve more people.

Chase's group raised about $27,000 to campaign against Prop. A, while proponents of the measure raised more than $2.5 million. Most of the proponents' money came from businesses and developers.

If her group was able to generate $25,000 more than it raised, it could have been successful, Chase said. She and other opponents had hoped to bring the extension to voters in 2006.

With the vote being so close, Chase had looked into the possibility of a recount, but said Friday her group simply didn't have the money.

The original TransNet was approved by voters in November 1987 and was first levied April 1, 1988. To date, the tax has generated more than $2 billion for transportation projects throughout the county.

It is expected to generate $3.3 billion by the time it expires in March 31, 2008.

Scott told the board Friday that the measure received more than 60 percent of the vote in all 18 cities in the county.

Contact staff writer Katherine Marks at (760) 740-3529 or kmarks@nctimes.com.