The first major connection between Picton and Christchurch could be open in just a matter of weeks.

The railway link has been closed since the Kaikoura Earthquake last year - and wasn't expected to open until at least November.

But Kiwirail CEO Peter Reidy said it could be up and running by the end of the month, which would immediately impact road traffic.

"If we can get the rail up by the end of August, we will be taking approximately 2000 trucks per month off the roads.

"To get this line up late August, I think is a real credit to our people and a real achievement for the local business owners in Kaikoura and Christchurch," Mr Reidy said.

State Highway 1 along the same route is expected to be finished before Christmas.