Passengers travelling to Greymouth on the Tranz Alpine train could have their travel plans disrupted this summer because the weather is too nice.

Already, one train has been held up because of the rail lines overheating, forcing the train to travel slowly, finally arriving at the Greymouth Railway Station at 3.15pm - two hours late.

On that occasion, heat sensors on the Midland Line showed temperatures on the rail lines reached 43degC.

Kiwi Rail says if the rail line temperature exceeds 40degC an inspection procedure is activated by the national train control centre before the passage of a train through the area. Track teams are also alerted and have to inspect the tracks before the train can continue its journey.


Kiwi Rail warns that over the coming summer months it is likely to impose speed restrictions on some sections of the line as a precautionary measure.

Southern regional manager Neil Campbell said railways throughout the world faced the same problem and must take measures to monitor rail temperatures to prevent any risk of track misalignment or heat buckling.

"While we regret any inconvenience to passengers travelling on our Tranz Alpine service, we cannot compromise on safety," Mr Campbell said.

Rail management in hot weather was an ongoing activity and could not be avoided, he said.

"We have been carrying out rail conditioning work, or de-stress as we describe it, for many years now to reduce the risk of buckled track in hot weather, but we can never eliminate it.

"These days we weld the rail up so that it has no rail joints, and then de-stress the rail to control expansion in the heat. There will be speed restrictions imposed where necessary to ensure the safe passage of trains," Mr Campbell said.

- The Greymouth Star