"We are aware that this is an important route for many motorists and we are working to get the road open as soon as we can," said regional performance manager Mark Owen.
Emergency services remained at the crash scene.
A detour was put in place, adding at least 30 minutes to the journey in and out of the capital.
Waikanae residents reported heavy trucks with big loads on small suburban roads that wouldn't normally see this level of traffic.
Frustrated motorists were asked not to take shortcuts.
"We ask that motorists stick to the signposted detour route as this is the most efficient alternative route to get the volume of traffic through that would normally travel on State Highway 1," said Owen.
The authority said the detour route was suitable for both heavy and light vehicles.
Police said the driver of the car had died at the scene and the driver of the truck had minor injuries.
A police spokeswoman said shattered fragments have now been moved off the train tracks and trains could now go through the area but at a severely reduced speed.
The serious crash unit is investigating the crash.
