A leading independent study has found that an in-built ventilation system on Manchester Metrolink’s M5000 trams helps to limit the risk of aerosol transmission of viruses, such as Covid-19. The system constantly circulates fresh air around the tram.
Transport for Greater Manchester commissioned global built environment and consultancy firm Arup to undertake Computational Fluid Dynamics (CFD) modeliing of the trams in what was the first study of its kind within the UK.
This modelling assessed the air flow within the vehicle and included particular focus on how this relates to the potential for aerosol transmission of viruses. It looked at how exhaled breath spreads through the vehicle and how that is affected by factors such as opening windows, mask wearing and activity levels.
The trams are ventilated through fans on the roof and air diffusers in the ceiling, with air exhausted from under-seat vent holes. Even with the ventilation system operating at half capacity, the study discovered that there were approximately 20 air changes per hour, which is better than the recommendation in a recent paper from the Scientific Advisory Group for Emergencies.
The study also showed that the risk of transmission is greatly reduced when face coverings are worn, while heavy-breathing – such as after a short run and/or loud talking and shouting – increase the risk of aerosol transmission. It was found that the risk of infection was reduced by around two-thirds by passengers wearing face coverings.
Danny Vaughan, TfGM Head of Metrolink, said: ““The safety of all those using Metrolink has, and will continue to be, our number one priority and the more we understand about how the virus is transmitted, the more effective our efforts in combating it can be. Studies like this and the recent study by Imperial College London on the effectiveness of cleaning regimes – like we have on Metrolink – demonstrate how we and our partners across the transport industry are taking an evidence-based approach to ensuring safer travel. With Step 2 of government’s road map now in place I hope these studies, coupled with robust cleaning and other additional measures we’ve introduced, help make people feel safe and confident as they return to our network.”
The findings of this study have now been shared with both the Department for Transport and UK Tram.