The traffic lights at the intersection of State Highway 1C Cobham Drive and Cambridge Road are now active.
Waka Kotahi said the changes would help peak hour traffic flow better.
Under the new intersection layout, traffic no longer has the option to turn right from Cambridge Rd into Cobham Dr. A raised safety platform at the intersection is designed to help keep vehicles at safe speeds.
Two new signalised pedestrian crossings and wider footpaths in some areas would help pedestrians, including tamariki attending Hillcrest School, cross these busy roads safely, Waka Kotahi said.