SAN DIEGO -- A plan to expand the trolley line north is back on track, 10News reported.

The line would run from Old Town to the University Town Center, and to build it would cost more than $1 billion.

However, some believe the benefit of the line is not worth the cost.

The red cars of the trolley are as synonymous with San Diego as Shamu is to SeaWorld.

The first link was the line to San Ysidro, arguably the most successful light rail line in terms of ridership.

The San Diego Association of Governments now wants to expand the line north 11 miles, from Old Town to University Town Center.

"We have more than 200,000 drivers on the road every day on that Interstate 5 corridor and with a new trolley system going up to UTC and UCSD we're going to be able to get a lot of people off the road," said Anne Steinberger of SANDAG.

Richard Rider of the San Diego Tax Fighters does not buy it.

"About three-quarters of the people who ride the trolley used to ride the bus, so that the idea that suddenly your roads thin out simply isn't true," said Rider.

With the exception of the San Ysidro line, Rider said the costs just don't pencil out.

Planners insisted going north will have an advantage that other expansions have not had.

"We'll be using the existing rail line to get much of this accomplished, so that's a big savings on the capitol costs," said Steinberger.

Rider said he is not convinced and cites the Sprinter as a prime example.

The Sprinter, Rider said, was budgeted for $52 million and came in at $500 million.

"The cost will always be more than they project, always," said Rider.

He also said ridership will always be less.

Transit officials said for the east expansion the green line over the last three years showed a sharp increase, especially between 2007 and 2008.

The north expansion would also have a stop at the University of California, San Diego -- definitely an advantage one UCSD researcher said is over her daily commute from Mira Mesa.

"The drive here in the morning and the drive back in the afternoon is really bad, so I figure I might as well take public transportation. I'd definitely use the trolley," said the researcher.

SANDAG said the north expansion could be operational by 2015.

Half of the cost would come from TransNet -- the half-cent sales tax -- and the other from federal transportation money if the project is approved.