High temperatures, delays and the London Underground: Is there a relationship? How might climate change impact its future infrastructural performance?

18:00 Tuesday 28 May




Sarah Greenham (United Kingdom) 1

1 - University of Birmingham

Transport infrastructure is both contributing to and affected by anthropogenic climate change. Rail infrastructure is particularly vulnerable to extreme weather events, and damage to rail networks results in negative socioeconomic consequences such as reduced work productivity due to loss of access to commuting. The London Underground (LU) by Transport for London (TfL) identified that extreme heat might have an impact on the network now and in future. However, these studies are limited to passenger comfort on the deep tube and do not focus on infrastructure or the vast majority of the network, which is in fact above ground. Therefore, this project, for the first time, examined the statistical relationship between high temperatures (by synthesising 2011-2016 industry data on delays) with air temperature data (from Met Office archives). A range of tests are presented between delay measures and variables to identify trends.

Results indicated that there are strong statistical relationships between most delay variables and high temperatures, particularly by mean daily frequency of delays and mean daily length of delays in minutes, though not causality. Some of the asset failures with the strongest relationships between high temperatures and delays are amongst the fleet on the Central line and signals on the District line. Track related delays, where rail research in terms of high temperatures is often focused (i.e. track buckling), did not demonstrate a strong relationship, suggesting that the LU network’s track is quite resilient. UK climate projections applied (assuming similar performance in future) suggested that the total annual number of delays under current conditions exceeding 24 degrees centigrade may increase from 4.5% to between 14.6% – 28.8% in frequency and from 4.4% to between 15.3% – 30.3% in length, depending on emissions scenario. Additionally, TfL measure delays in a unique calculation named ïlost customer hours’, and though showed a relationship with high temperatures, accounts for externalities which limits its suitability the context of this project. Therefore, future recommendations include reviewing how delays are captured for future analysis, which may enable benchmarking and comparative analyses between networks.

Further research is required by LU asset and the wider environment in detail to understand how high temperatures cause their failures to identify how they can be mitigated from such hazards in future. Some results from this project have been presented in two public forums: TfL’s Safety, Sustainability and Human Resources Panel (28/02/2018) and the House of Commons Environmental Audit Committee (15/05/2018).