The contractor made the traffic changes after 8 p.m. Wednesday (March 13).
Southbound traffic is diverted to and from the northbound lanes by temporary median crossings, according to the Arkansas State Highway and Transportation Department.
"Drivers can expect to have a little more congestion at times," said Joe Shipman with the AHTD.
Temporary ramps allow access at all interchanges.
The change allows crews to remove and replace bridges and overpasses at four locations along the construction zone, as well as other improvements.
"We have several bridges on this section of highway that date back to the early 1960s," said Shipman. "We've done fairly heavy maintenance to them over the past several years."
After closure of the southbound lanes, removal of the bridge over Grand Avenue will begin with lane closures between 7 p.m. and 6 a.m. and short-term lane closures of less than 30 minutes between midnight and 5 a.m., according to the AHTD.
Students at University of Arkansas - Fort Smith say the construction on I-540 has affected their ability to get around town, and the traffic has them seeking alternative routes.
Matthew Mooring, a UAFS student and Fort Smith native, said he's avoided I-540 since the construction began.
"It usually takes me about two to three minutes to get to where I'm going," said Mooring. "Now it takes me about 15 minutes to get there, and it could take anywhere to about 45 minutes. The traffic is usually at a standstill."
UAFS student Johnathan Sammons works in Ozark on the weekends. He says he will likely take an alternate route through Barling as a result of the traffic changes on I-540.
Shipman said 25 percent of motorists who typically drive I-540 have opted for other routes.
This stage of work is expected to take four months to complete. The entire project is expected to be finished by mid-2014.
The speed limit has been reduced to 55 miles per hour in the construction zone.