As a passenger on public transport, you may wonder why air conditioning is still important for winter travel. Air con is something many people associate with the often-stifling heat of summer – but when you’re travelling in a confined space with lots of other people, passenger comfort is the key to having a pleasant journey, yet one of the most-asked questions public transport operators see on their social media feeds is, “Why is the air conditioning on when it’s cold outside?”
This is a valid question, as when the weather is cooler, it seems odd that train operators still need to have the AC on, particularly if the windows are closed because it’s chilly outside.
A train is an enclosed space, so the heating, ventilation and air conditioning system must be kept on to ensure adequate air circulation for passengers and the crew.
Even if the weather is chilly, you would be surprised at how quickly a rail carriage can feel stuffy and warm, especially when the windows are closed and there are many people inside, whose bodies are generating heat at the same time.
Air con also has the very important job of keeping our surroundings dry. If the carriage is warm and humid, with condensation on the windows, this kind of environment is more likely to promote the growth of bacteria.
Having the AC working prevents the build-up of moisture on board, combats the spread of bacteria and prevents the odours that can be part and parcel of a packed train or tube.
Rail operators will pre-set the temperature for passenger areas so that it accommodates the needs of the average person, with the aim of setting it at a temperature that will feel comfortable when the train is around 50% full.
Adjusting the temperature
Continually monitored and regulated, based on how it feels inside the train, the temperature will fluctuate when people get on and off, and when there aren’t as many on board.
Passengers who find the temperature is unbearable can notify the rail operator, who can adjust it within a pre-set range. However, what one passenger finds too cold might be okay for another.
Airborne virus transmission
Another reason why clean air and ventilation are important, especially in winter, is to reduce the concentration of any viruses, such as Covid-19, in the air. The AC system minimises the risk of airborne transmission, which can occur when people in an enclosed area breathe in small particles after someone with a virus has been there.
Using air con doesn’t mean it has to be cold on public transport to provide adequate ventilation and cleaner air. It means striking a balance between keeping the interior air at a pleasant temperature and making sure it is as clean and healthy as possible.
Scientific research has revealed railway air conditioning improves the trains’ air quality. Attributed to the trains having AC systems equipped with air filters, according to a study published in Science Direct, the concentration of particles in the air inside the trains is generally lower than on the platforms.
Research has been carried out in both warm and cold weather. On an average rail journey of 30 minutes, air-conditioned carriages contain up to 50% fewer particles than carriages without air con. For train drivers and other rail workers, who spend many hours a day within the train, the use of air conditioning is even more important than it is for the commuting public.
Virus prevention research
A report by the UK’s National Engineering Policy Centre has revealed details of potential new engineering approaches to reduce the risk of Covid-19 transmission on public transport. The report noted how HVAC systems on trains were used to remove general atmospheric dust, diesel fumes and other dust and odours from the interior.
The international standard for ventilation and heating in intercity rail coaches is based on keeping the interior of the carriages at a comfortable 22°C (known as a “shirt sleeves” temperature) in winter and at a maximum of 27°C in summer. The AC system must maintain minimum quantities of fresh air per person.
Viruses live longer indoors in winter, because the air is less humid than outside – so this further reinforces the importance of air con on public transport in winter.
Currently, research is ongoing into whether operators can retrofit filters or other devices into existing rail HVAC systems to improve the air quality even further. Some developers have suggested software modifications, enhanced filtration such as HEPA filters, or the electrostatic treatment of the airflow.
Feasibility studies are exploring how well these air cleaning technologies would function. The aim is to ensure any virus particles will be completely destroyed as they pass through the train’s HVAC system.
All things considered, air con is an absolute MUST on our rail transport system in winter, regardless of the weather conditions!