A warning system designed to improve road safety at the turnoff from State Highway 1 to the Moeraki boulders is operational and the variable speed limit is legally enforceable.
Associate Transport Minister Tim Macindoe said the new system installed on SH1 detected vehicles approaching the right turning bay at Moeraki Boulders Rd and vehicles waiting to turn back on to the highway.
When vehicles are detected in the area, an electronic sign shows the speed limit reduces from 100kmh to 70kmh to allow the approaching car to merge safely with oncoming traffic.
The 70kmh variable speed limit applied to 170m either side of Moeraki Boulders Rd, he said.
The variable speed limit would help reduce the severity of crashes at the turnoff by lowering the speed of highway traffic, while maintaining the 100kmh speed limits when the intersection was not in use. The system was a ''great alternative'' to permanently reducing the speed limit in the area, Mr Macindoe said.
Crashes on the stretch of highway between the Waitaki River Bridge and Dunedin from 2006 and 2015 had resulted in 21 deaths and 114 serious injuries, he said.
''While road safety is everybody's responsibility, the Government is committed to making these roads and roadsides safer to help prevent further tragedies.''
The variable speed limit became enforceable on Thursday.
