Truck lanes proposed for a toll road project on I-75 in Cobb County have dropped off the table because the project grew so expensive, its developers said at a meeting at the state Department of Transportation Thursday.

That developer team and five others who propose toll projects for metro Atlanta made their cases for reviving or continuing their projects at the all-day meeting.

They have endured months or years of delay on proposals submitted in response to a Georgia law inviting private investment in public toll roads, passed in 2003 and revised in 2005.

Commissioner Gena Abraham asked her team to re-evaluate the toll program, and in April a financial adviser to DOT recommended that DOT stop work on those proposals.

David Doss, chairman of the committee that deals with such projects, called the meeting as "an opportunity for them to come and resell, if that's the right word, their proposals."

Developers of the I-75 project, led by Bechtel Infrastructure Co. and Kiewit Southern Co., are looking at lower-cost alternatives to their original proposal. DOT has made no decision to eliminate the truck lanes, Doss said. But changes to the project and inflation have sent the estimated cost from $1.8 billion to $4 billion, a price the state can't pay. That project is the only one under contract, for $38.5 million in preliminary work.

The other projects are on Ga. 400 and on I-285's western wall.

All of the proposals envision adding toll lanes to the side of a highway separate from the regular lanes. They could be optional lanes with tolls that rise with congestion, for people willing to pay for a faster ride.

Some board members opened the door for a discussion of adding tolls to existing, free lanes.

Board Chairman Bill Kuhlke said tolling the existing lanes "would have a tremendous impact" on the amount of money a project could bring in. "But politically it's probably a hot rock," he added.

A spokesman for Gov. Sonny Perdue, Bert Brantley, said that Perdue supports the concept of bringing private capital into transportation but there are "a lot of unanswered questions" about how the projects could fit together into a seamless whole.