Gwinnett County will give a company an extra year to decide whether it makes sense to build a toll road that would connect Ronald Reagan Parkway to Interstate 85.

The Board of Commissioners voted unanimously Tuesday to grant the one-year extension to Skanska USA Civil Southeast, which is studying the $257.5 million project that could shave commute times for South Gwinnett residents.

It’s the third time Gwinnett has given the company extra time to complete the study, first commissioned in 2009.

Gwinnett Transportation Director Kim Conroy said the extra time is needed to study the impact that a new Ronald Reagan interchange would have on I-85 traffic and to study ways to better manage traffic on the interstate. The state Department of Transportation, which also is involved in the study, asked Skanska to study I-85 after Gwinnett launched its own study of extending Ronald Reagan.

Advocates say a Ronald Reagan Parkway extension could make it easier to reach some commercial areas and help South Gwinnett commuters stuck in traffic during rush hour. The four-lane divided highway runs from Scenic Highway in Snellville to Pleasant Hill Road near Lilburn, stopping three miles short of I-85.

With money scarce, Gwinnett sought a private partner to build and pay for the project. Now Skanska is studying whether it makes sense for the company to extend Ronald Reagan to I-85 and convert the new section into a toll road. The company also is studying possible routes, toll prices and whether any public money is needed.

Gwinnett is paying $1.4 million of the $2.6 million cost of the study, with Skanska paying the rest. The latest delay in the study won't cost Gwinnett more money, Conroy said.