Don't expect special carpool lanes to appear on Interstate 26 anytime soon.

While the Charleston portion of I-26 -- specifically the stretch between Montague Avenue and U.S. Highway 78 -- seemed the most-promising stretch for High Occupancy Vehicle lanes, a new study concluded that retrofitting the interstate for such lanes isn't feasible.

Twenty-two states have at least one major commuting corridor with special lanes available for cars with more than one passenger during rush hours, but not South Carolina.

The S.C. Department of Transportation looked at the pros and cons of creating such lanes at five locations, including I-26 in Charleston, I-385 in Greenville and three interstates in Columbia.

The Charleston stretch showed the most promise of all five sites, and an in-depth study looked at congestion, partly by analyzing cars' speed based on cell phone signals, said Richard Day of Stantec Consulting, which worked with the Transportation Department on the project.

Day and Doug Frate, chief transit planner with the Transportation Department, presented the findings of their study Monday to the Berkeley-Charleston-Dorchester Council of Governments.

As many commuters know too well, the interstate slows significantly around Interstate 526 during the morning and evening rush hours.

However, creating a carpool lane would require narrowing existing lanes from 12 feet to 11 feet and cutting into the emergency lane, making retrofitting a less-appealing option, Day said. "We have some concerns, to be honest about it," he said.

Projections have shown that sections of I-26 will fail to handle daily traffic loads by 2030, even after they're widened.

The study also looked at the possibility of creating "hot lanes," which would be restricted to high-occupancy vehicles and single-occupancy cars whose drivers have paid a toll. Day said "hot lanes" would not pay for themselves until 2038.

North Charleston Mayor Keith Summey, who chairs the Council of Governments board, said the agency will receive the study as information.