Upgrading work began this week on the Southern Ports Highway and Southend Access Road junction.
It is located midway between Rendelsham and Beachport and the work includes a left turning lane at the cost of $400,000.
It is being undertaken by Wattle Range Council on behalf of the Department for Infrastructure and Transport.
Council and the Southend Progress Association have lobbied for the lane for several years in the interests of road safety.
Speed and lane restrictions will be in place during work hours, and local access will be maintained.
Motorists are asked to follow traffic controls when in the area. Works are scheduled to be completed by the end of March.