Rail passengers across the UK are experiencing significant disruption as the country endures a period of extreme heat. Several major operators, including Great Western Railway, Avanti, and LNER, have advised passengers to only undertake essential travel, particularly on routes affected by the severe weather warnings. This guidance comes as a 'heat-dome' settles over Western Europe, pushing temperatures into dangerous territory for infrastructure.
Network Rail highlights that hot weather presents challenges as severe as those posed by freezing winters. The primary concerns revolve around the steel tracks, overhead power lines, and the ground supporting the railway. Steel tracks, which form thousands of miles of the UK network, can absorb heat up to 20C higher than the ambient air temperature. While most of the network can operate with track temperatures up to 46C (equivalent to approximately 30C air temperature), temperatures have been recorded as high as 51C on the rails.
As steel expands when heated, the rails lengthen, creating immense tension against adjacent sections of track. If there is insufficient room for this expansion, the rail can buckle, necessitating the closure of lines for repairs before services can resume safely. This phenomenon, known as 'buckling', is a significant structural distortion where the tracks warp or bend due to extreme heat.
Furthermore, overhead power lines, which provide electricity to approximately 44% of all passenger trains in the UK (including major routes like the East and West Coast Main Lines), are also vulnerable. In hot conditions, these lines can expand and sag. When this occurs, temporary speed restrictions are imposed to reduce the forces exerted on the tracks and minimise the risk of dewirements, where the pantograph on a train catches on a sagging line.
John Lawrence, Chair of the Institution of Engineering and Technology Railway Technical Network, emphasised that track buckles and dewirements are critical concerns for engineers, despite ongoing investment and improvements. He also noted 'hidden failures' that can arise from heat stress, affecting signalling control systems, power supplies, and trackside telecommunications. Lineside fires, potentially sparked by anything from discarded litter to passing trains, can further exacerbate disruption.
To combat overheating, rail operators employ various strategies. These include painting tracks white, a measure that can reduce track temperatures by up to 5C, and lubricating rail joints to facilitate expansion. Temperature sensors on rails and thermal imaging from drones and helicopters are also used to identify overheating equipment, allowing for proactive repairs, often carried out overnight. The Met Office has issued rare red weather warnings for parts of England and Wales, indicating potential significant disruption and danger to life, underscoring the severity of the current conditions.