Tar Barrel Tunnel Bypass

The Main North Line, running between Picton and Christchurch, is a key freight route primarily moving domestic products from Auckland to Christchurch and beyond.  The Great Journeys of New Zealand Coastal Pacific service also operates on this line over the summer months.

Tunnel 21, at Tar Barrel just south of Ward, is the oldest tunnel on the line. Damage caused during the Kaikoura earthquake has been repaired, however a lot more work is needed to bring it up to a modern standard. Its small size means trains must slow down to go through it, which lengthens journey times on the line and causes operational constraints.

KiwiRail is working with Waka Kotahi NZ Transport Agency to eliminate the tunnel to improve rail operations and seismic resilience for both road and rail.

To do this, the rail line is being realigned away from the tunnel and a road overpass constructed across the tracks for State Highway One.



Tunnel 21

Work is underway and involves:

• Rebuilding one kilometre of rail track through a cutting that requires the removal of approximately 450,000 cubic metres of material;

• Short temporary diversion of State Highway One while the road overpass is built.

Finalized Tunnel 21 Web Graphics long strip for web 002 v2

Eliminating the tunnel means higher speeds for trains and removes a vulnerability both for rail and State Highway One above it.

The project is expected to take about 18 months to complete.

The rail line will be realigned to run east of the existing tunnel.

view looking south