Part of Main South Rd has been reduced to one lane since March while underground pipes are replaced and the traffic has flowed towards Dunedin.
The Dunedin City Council has agreed to switch the direction, away from Dunedin and towards Brighton and Mosgiel, after discussions with Green Island business owners.
The change has yet to be implemented.
Fresh Choice Green Island supermarket owner John Moyle said he hoped the change would suit "homeward traffic" from Dunedin that had traditionally stopped in Green Island.
Businesses there tended to benefit from trade after school and after work, he said.
The reversal in Main South Rd will be in place until a full road closure from mid-August, to enable a roundabout to be built.
The city council has been replacing underground pipes and it is raising three pedestrian crossings in Main South Rd.
Installation of the roundabout at the intersection of Main South Rd and Church St is due to happen between mid-August and mid-October.
The overall project will cost about $2.4 million.
Dunedin City Council transport delivery manager Ben Hogan said the one-way directional switch would be made soon, possibly mid-June.
The city council would first need to discuss with the Otago Regional Council how bus stops would be affected.
After the change, motorists travelling towards Dunedin should use the motorway or Abbotsford roads, Mr Hogan said.
"We don’t encourage the use of narrow residential streets in Green Island as a detour route."
Night ’n Day shop owner Antony Duthie said he was worried the switch in direction might come too late, after people had already got used to different travel habits.
"Hopefully, we do see an increase in business."
Mr Duthie, also the Greater Green Island Business Association chairman, said meetings had been held with the council and contractor Fulton Hogan.
City councillor Andrew Whiley said he understood trade there was more likely to come from customers travelling from Dunedin towards Mosgiel than the other way.
"A lot of people stop into Green Island on their way home, especially after 3pm."
