Otago Southland Coroner David Crerar found fruit-pickers Chin Yuan Chang, of Taiwan, and Ting Ting Mo, of China, died after Mr Chang failed to give way while turning right at the intersection of State Highways 8B and 6 at 6.15pm on January 12, 2012.
The car he was driving collided with a southbound van on SH6.
Mr Chang died at the scene and Ms Mo died in Dunedin Hospital at 1.05am the next day.
Three other passengers in the car were all injured. The van driver received minor injuries. The New Zealand Transport Agency (NZTA) had been reviewing the speed limit at the intersection before the crash and afterwards had dropped the limit to 80kmh from 100kmh.
It had since bought land from a neighbouring vineyard and created a new left-turning lane to further separate left-turning and straight-through traffic, to increase visibility for those turning right, as Mr Chang had been.
Mr Crerar ''noted and commended'' the improvements in his findings.
He recommended the agency review the speed limit again ''to ensure the appropriate safe speed limits for the intersection is continued'' and continue monitoring the crash site to ensure the safety improvements ''remain appropriate''.
Mr Crerar said while the exact speed of the vehicles could not be confirmed, Serious Crash unit investigator Senior Constable Alastair Crosland established the van was travelling at less than 70kmh and Mr Chang was driving about 21kmh across the intersection.
It was thought Mr Chang slowed at the intersection but did not give way, as the give way sign obliged him to.
There was some evidence from surviving passengers that Mr Chang may have been tired.
He had a blood alcohol level of 17mg, less than a quarter of the legal limit.
''Whilst motor skills may not be affected by alcohol consumption, an already tired person may become sleepier after drinking even a modest amount of alcohol. The crash is the subject of a momentary lapse in attention, which could be related to tiredness, but it has had tragic consequences,'' Mr Crerar said.
He said he attributed no blame for the crash to the van driver.
NZTA Central Otago area manager John Jarvis said he had yet to see the report but would be ''taking note of it''.
He said the agency always monitored sites such as that intersection and since the redevelopment, he had heard a lot of positive feedback.
He said he was not aware of any more crashes there since the redevelopment.
