Imagine the unthinkable.

Trains ferrying commuters from the heart of Atlanta all the way home to Cobb or Gwinnett counties. An I-285 interchange flowing free at rush hour. North Fulton commuters breezing up Ga. 400. Reliable workday drive times.

Proponents of a new penny sales tax for regional transportation dream of putting metro Atlanta in the big leagues of modern transit and roadway systems. Some of those visions are already emerging as cities and counties assemble their wish lists of projects, which are due to the state March 30.

But if next summer's 10-year, 1-cent regional transportation referendum is to succeed, it will take collaboration by elected leaders on a final list that has something for everyone, Atlanta Regional Commission Director Chick Krautler said.

There's evidence of this happening. As they compile lists, several jurisdictions have reached across county lines to compare notes, in some cases endorsing projects outside their borders.

Fayette County, for example, plans to support a $22.5 million interchange upgrade at I-85 and Ga. 74, which is in the Fulton County city of Fairburn, Public Works Director Phil Mallon said.

Douglas County will endorse Cobb County's proposed $26.5 million widening of Ga. 6, adding truck-friendly lanes, Transportation Director Randy Hulsey said. Douglas will also endorse Cobb's bus route and transit proposal for Veterans Memorial Highway, and it might even nominate adding sorting lanes on I-285 between I-20 and Bolton Road, which is in Atlanta, Hulsey said.

Such regional thinking is a good sign for this stage in the process, Krautler said.

"Right now, it seems like the cooperation is quite good," he said. "I haven't heard of any breakdowns."

But alongside cohesion, discontent is brewing. While business and political leaders see the referendum as a last hope, Vangie Watkins views it as backward and unfair.

The south Fulton resident, well familiar with the logjams near her home at I-285 and Cascade Road, said she doesn't see how her county will get a fair share of the roughly $8 billion that the tax would generate over 10 years. Not with projects being funneled through the DOT, then through committees where suburban politicians hold the majority, she said.

"What if they don't pick any projects from my area?" said Watkins, who has railed against the tax at two public meetings. "It's like the lottery."

Fayette County Commissioner Steve Brown said his county -- one of metro Atlanta's least-dense counties, with the fewest linear miles of road and no interstate -- wouldn't benefit.

"They need help paying for them, and we have become a revenue source," said Brown, who rode into office in November on a platform that called for keeping Fayette transit-free. .

Clayton County is admittedly lagging in the nomination process.

“This is really late," Commission Vice Chairman Wole Ralph said at Tuesday's meeting. "We haven’t yet received the projects."

Nominations are due to DOT Planning Director Todd Long by March 30. He will spend the next two months weeding out projects that don't meet criteria -- such as those lacking regional impact -- and will turn over an "unconstrained list" to the Atlanta Regional Roundtable by June 1.

The roundtable, made up of 21 mayors and commission chairmen, will approve a final list by Oct. 15.

“We had a shallow window of time to put these in,” Clayton Commission Chairman Eldrin Bell said. “Other counties have full staff devoted to this."

Clayton Transportation and Development Director Jeff Metarko told The Atlanta Journal-Constitution that some two dozen projects have been discussed. The transit issue, controversial in Clayton because residents want it but the county has been resistant to provide it, is up in the air.

“We have discussed bringing commuter rail to Clayton,” Metarko said. “It’s not like MARTA. It’s the commuter rail that’s been discussed for years.”

Transit threatens to be a wedge issue, with some suburban residents resistant to having it in their communities and DeKalb and Fulton counties bitter that they already pay a penny tax for MARTA. DeKalb and Fulton mayors have said that unless a governance system is established for a metrowide mass transit system -- eliminating the stigma of MARTA -- they don't believe their voters will support the referendum.

Brown, of Fayette County, said the regional plans will usurp counties' control.

But other suburban leaders say their voters are ready for rail. A study conducted last year showed that 51 percent of people were seeking an alternative transportation option to riding in their cars, Cobb Commission Chairman Tim Lee said.

Polls have also shown Gwinnett residents, who voted against MARTA decades ago, want rail transit now, said Chuck Warbington, executive director of the Gwinnett Village Community Improvement District.

“Most definitely things have changed,” he said. “I think people realize that you can’t continue to build just roads to help congestion.”

Staff writers Ariel Hart and Janel Davis contributed to this article.

The wish lists: A sneak peek

A sampling of what some counties and cities have on their wish lists of transportation projects to be submitted to Todd Long, the planning director for the Georgia Department of Transportation Planning Director Todd Long, with estimated costs:

Cobb County

  • Creating a high-capacity transit system, likely light rail, in the U.S. 41/I-75 Northwest Corridor from Acworth to MARTA's Arts Center Station: $2 billion
  • Widening Cobb Parkway/U.S. 41/Ga. 3 to six lanes from Paces Mill Road to North Marietta Parkway: $230.3 million

Fayette County

  • Making roadway and intersection improvements to the East Fayetteville Bypass, from Ga. 85 to South Jeff Davis Drive: $39.4 million
  • Making efficiency, connectivity and safety improvements to Hood Avenue Connector, from Ga. 92 to North Jeff Davis Drive: $9.6 million

Fulton County

  • Widening Cascade-Palmetto Highway from Campbellton Road to Campbellton-Fairburn Road: $36.8 million
  • Improving the interchange at I-285 and Cascade Road: $20 million

Gwinnett County

  • Creating four light-rail sections -- from the Doraville MARTA station to Norcross, from there to the Indian Trial Park-and-Ride lot, from there to Gwinnett Place, and from there to Gwinnett Arena: $954.75 million
  • Rebuild three grade separations (height variations at junctions) on Ga. 316 at High Hope Road/Cedars Road, U.S. 29/Ga. 8 and Harbins Road: $142.6 million
  • Widening Ga. 20, from Peachtree Industrial Boulevard to the Chattahoochee River bridge: $47.6 million

Alpharetta

  • Adding operational improvements (landscaped median, bike lanes, sidewalks) to Rucker Road from Hardscrabble Road to Wills Road: $19 million
  • Extending the Big Creek Greenway from Marconi Drive to Forsyth County: $11 million

Sandy Springs

  • Widening Hammond Drive between Roswell Road and Ga. 400: $40 million
  • Adding sorting lanes on Ga. 400 north of I-285: $140 million

The road to the referendum

The 10-county Atlanta region is facing a referendum in 2012 to vote on a list of transportation projects, and a 1 percent sales tax to fund them. Regional officials say the tax, likely to raise $8 billion over 10 years, could represent the region’s biggest single infusion of infrastructure funding since the MARTA tax and the gas tax were raised 40 years ago. The Atlanta Journal-Constitution is following the story as the local elected officials put together the project list, and business and civic groups mount a campaign to sell it.