Cobb residents will have to wait a little longer to find out the suggested transit mode for the county’s congested northwest corridor.

A study of the area revealed seven alternatives, ranging from a no-build option, to express buses, to a light rail and bus rapid transit combination. But a final recommendation is not expected until late August or September. And some skeptics in the county who have long thought that county leaders have favored light rail for the area were already doubting the outcome.

The preliminary results of the Northwest Transit Corridor Alternatives study, intended to find transit alternatives along I-75 and US 41 (Cobb Parkway) in the northwest part of the county into Atlanta, were released during an open house Tuesday night in Marietta.

The study examined four routes: two starting in Acworth and two starting at Kennesaw State University, and each running to the Arts Center MARTA station in Atlanta. One proposed route from each starting point would run along Interstate 75, while one would run along Highway 41, or Cobb Parkway.

The $1.9 million AA study project began two years ago when the county applied for a federal grant that would help pay for it. . The project officially began in August 2011 and is about 80 percent funded with federal dollars. Cobb County chipped in almost $206,000, and the county’s cities, community improvement districts and Kennesaw State University also contributed.

The study has become a lightning rod in Cobb, with groups for and against transit and the upcoming regional transportation referendum using the report to make a case for their side. Cobb chas a $689 million bus rapid transit project on the transportation list voters will have the chance to approve or reject in July. The 10-county vote is seeking a one-cent sales tax that would pay for more than $6.14 billion in transportation improvements. If the final study recommendation — which would require regional and federal approval — were light rail, it wouldn’t change the bus project, but could enhance it, said Faye DiMassimo, Cobb’s transportation director.

Light rail is an unnecessary expense, opponents say. For the county to get the best value for its money, the best option is express bus lines using existing high occupancy lanes and that could run along the reversible lanes that are planned for I-75/I-575, said Cobb resident Ron Sifen, who has frequently spoken out against the high cost of light rail. But that option is likely not to get a favorable review in the final recommendation, he said, because officials have made light rail a “predetermined conclusion” for the county.

“My initial look at the study confirms there has been a thumb on the scale and it doesn’t take an expert to read the fingerprints,” said state Rep. Ed Setzler (R-Acworth), who agreed with Sifen about the report's slant. Setzler has supported running a commuter rail on the existing CSX train line from the north part of the county, but that option was found by project reviewers to be unfeasible.

Tuesday’s open house was attended mostly by people associated in some way with the study, or vocal community leaders on transportation issues.

Powder Springs resident Joseph J. Bushell was one of the few residents at the event with no connections to the study. Bushell, 35, found out about the event through a link on Facebook and brought along his father to find out more.

Both Bushells, immigrants from England, were in favor of light rail for the county because of its accessibility, smooth ride and attractiveness over buses for residents.

"All of this is for the future, I'll be dead and gone probably when this happens, and I'm OK with that and I don't mind paying for it," said the senior Bushell. "But we need to be looking there in that direction now."