Where and how often do people touch train interiors? An investigation during the pandemic

The coronavirus disease-2019 pandemic highlighted infection and hygiene as risks in dense public spaces, including public transport vehicles. This study investigated passenger touching behaviour within metro vehicles to understand the fomite exposure of passengers. Using in-vehicle CCTV on three lines of the London Underground, this paper investigated the number of touches on different types of train interiors and investigated their relationship with passenger density and movement. In total, 1818 station sections and 16 891 passengers were observed cumulatively from May to December 2021. The results showed that on average for each type of interiors on Victoria and Jubilee lines, there were between 0.07 and 0.57 touches per passenger movement (i.e. boarding or alighting) for deep tube lines, whereas District line that uses larger carriages showed a different tendency. The results also suggested that for deep tube lines, the number of touches per person increased beyond a density of similar to 1.5 standing passengers/m2 possibly because passengers may touch interiors more in order not to bump into other passengers. These findings can be used in infection risk modelling and can inform mitigation of infection risk of future pandemics.