Here's how Network Rail is preparing for 'record-breaking' temperatures on Portsmouth to London line

Network Rail are expecting the mercury to ‘exceed 35 degrees’ on parts of its major routes including Portsmouth to London Waterloo tomorrow.

The national railway infrastructure manager has activated its ‘extreme weather action teams’ on the South Western Railway network.

These teams work to minimise heat-related infrastructure problems and keep passengers moving safely.

The rail network is made of steel track which absorbs heat easily. In direct sunshine rails can exceed 50 degrees, causing them to expand. In extreme cases, when rails cannot expand any further, they can buckle.

To reduce the likelihood of buckling, in the most vulnerable locations during the hottest times of the day, speed restrictions may be introduced as slower trains apply lower forces to the rails.

To prepare for these high temperatures Network Rail have painted the most at-risk rails white, so they absorb less heat, reducing temperatures by up to 10 degrees. Cooling equipment has also been fitted to a number of other key assets across the Wessex route.

David Dickson, managing director for Network Rail’s Wessex route, said: ‘With temperatures expected to exceed 35 degrees across the route this week, getting passengers to their destinations safely is our top priority.

‘We will be doing all we can, along with our colleagues at South Western Railway, to keep passengers moving safely and comfortably throughout the heatwave.’

Passengers travelling via London Waterloo or Clapham Junction can top up water bottles at free refill points.

There are two refill points at Waterloo, located on The Balcony adjacent to Platform 1 and on the ground floor concourse located next to Exit 2. At Clapham Junction a refill point can be found next to the main entrance barriers.

If you feel unwell before you start your journey, please do not travel. If you feel unwell while travelling, please get off at the next stop and speak with a member of staff.