Your questions about how severe weather affects Southern services answered here…
Why do 'leaves on the line' cause problems for train services?
Thousands of tonnes of leaves fall onto the railway lines each autumn. These leaves are compressed by passing trains to create a thin, slippery layer on the rails, so drivers have to brake earlier when approaching stations and accelerate more gently to avoid wheelspin. The leaf mulch can also insulate the 'third rail' that our trains draw their power from.
Network Rail works hard to cut back tree branches and plants along the trackside and has specialist vehicles to try and keep the tracks clear during autumn. However, despite their best efforts, during the period when most trees shed their leaves there will be some problems.
Why do snow and ice cause problems for train services?
UK train services are vulnerable to snow and icy weather conditions because they draw power from a third rail running alongside the track.
When the rails are covered with a layer of ice it can act as an insulator, making it difficult for the trains to draw power and move.
We work with Network Rail to do what we can to stop the ice forming in the first place. We run de-icer trains and 'ghost' trains (empty trains) throughout the night to try to stop the ice from forming, but despite our best efforts, ice will form in freezing temperatures and trains sometimes become stuck or fail.
We're guided by Network Rail, who manage the UK's railway infrastructure, about when it is safe for us to run trains on their lines.
Why do train services get disrupted during the summer?
The extremes of our summer weather – from high temperatures to prolonged rainfall – cause problems for the rail network such as the risk of line-side fires and buckled track.
On hot days, rails in direct sunshine can be as much as 20°C higher than the temperature of the air. As rails are made out of steel, they expand as they heat up and are subject to strong compression which can cause the track to buckle.
If this happens, the line must be closed and the track repaired before services can start again, which we know causes considerable disruption. Usually, these repairs can't be done until the temperature of the rails has dropped.
If a section of track is judged to be at risk, we introduce local speed restrictions – slower trains put lower forces on the track and reduce the chance of buckling.
What are your compensation arrangements for weather related disruption?
You can claim compensation under our Delay Repay scheme if your journey is delayed by more than 15 minutes for any reason other than planned engineering work.