Train speed restrictions for Wairarapa as heat causes derailment risk

Inspectors are carefully checking train tracks to make sure the heat hasn't caused misalignment. Photo / File

Even the trains are slowing down as temperatures rise in the lower North Island, with fears of the tracks being warped by heat.

The Wairarapa line is under a speed restriction at the moment to protect against incidents or derailments caused by misaligned tracks.

"When it gets to a certain temperature [the rails] start to expand," said Kiwirail acting group manager of network services Henare Clarke.

"When it goes above that 55C there's going to be some point where it's going to try and misalign.

"In winter we have the opposite effect where, as it cools right down and temperatures drop, it actually contracts. We have the opposite where we would get breaks in the track."

There are heat sensors on the tracks to monitor when the rails reach 40C or higher.

If that happens, inspectors head out on "heat runs" to check the tracks for any warping, and some sections of the line are placed under speed restrictions. This is the case for the whole country.

Under the restrictions, trains can only travel at 40km/h.

When temperatures go above r55, blanket speed restrictions are placed on the lines, Clarke said.

"It doesn't give the track much time to cool down overnight, it stays at quite an elevated temperature.

"There's just no hiding from the heat at the moment.

"We will do what is necessary to make sure that we don't have any incidents on it. That blanket ban is probably the last resort for us but we will put it in place if the temperatures exceed.

"At the end of the day, safety is paramount for us."

While the train tracks are heating up, Wellingtonians are finding other ways to cool down.

Lower Hutt residents will be able to stay cool for longer as the hours of Hutt City Council's summer pools are extended to 8pm most weekdays until further notice.

The Wellington City Council has also put out a handy list of tips for people to fight the heat.

The tongue-in-cheek lists tells men putting a bowl of ice cubes down their pants will "lessen the impact of these hot afternoons and be a conversation starter".

It also suggests people shout each other icecream sandwiches, jump in the harbour fully-clothed, and use the power of thought to cool down.

Slightly less wacky suggestions include visiting the unheated Khandallah pool, drinking coffee over ice, and putting pillows in the freezer 30 minutes before bedtime.