Transit: It’s Time to Vent

Mercat Nou Station, Line 1, Metro Barcelona featuring two ventilation ducts.

The CDC (Centers for Disease Control) has stated that airborne transmission of the coronavirus is more likely than transmission through surface contact. Adequate ventilation and air filtration of HVAC systems can reduce the likelihood of airborne exposure. Every transit agency wants to do everything it can to keep its ridership safe, healthy, and returning. The multi-trillion-dollar, pandemic-clouded question is, how?

Can we just eliminate the word normal from the lexicon? Face masks. Temperature screenings. Physical distancing. Photocatalytic oxidation. Ultraviolet germicidal irradiation. Really? Can’t we just go back to convincing everyone to get out of their cars? No, unfortunately we cannot. Once again, like after 9/11, transit agencies must adapt to a new normal. And this one will prove no easier.

At present, it is an “unfare world.” The numbers could not be more dire. A March 2020 EBP (formerly Economic Development Research Group  U.S.) study reported that ridership throughout the U.S. was down 73% nationally; fare revenues were off 86%. EBP projected revenue losses of $26 billion-plus for 2020 and $24 billion-plus for 2021. That’s not good. Though the transit industry received $25 billion for operating expenses as part of the U.S. government’s Coronavirus Aid, Relief and Economic (CARES) Act, the study cites a funding shortfall of nearly $24 billion by the end of 2021. Nearly 40% of all annual transit budgets derive from fares and other ridership-related revenue. So, transit executives know that winning back ridership is paramount to survival. Multiple strategies have been proposed to do just that, but everything rests on convincing the riding public that it is safe. And one critical element in any safe return is the absolute certainty that the air in transit facilities won’t infect riders. 

“Although much remains unknown about COVID-19, scientists have established that the coronavirus is highly contagious and transmitted via air,” relates the July 2020 McKinsey & Company article, Can HVAC Systems Help Prevent Transmission of COVID-19? “Studies suggest that it primarily spreads when infected people cough, sneeze, or talk…Given the concern about airborne transmission, building managers, safety experts, and others might take steps to optimize ventilation and airflow indoors and limit viral spread.”

They are not alone in that belief. The American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) believes that HVAC will play a critical role in helping to prevent the spread of COVID-19. In its April 2020 ASHRAE Position Document on Infectious Aerosols, ASHRAE states, “Dilution and extraction ventilation, pressurization, airflow distribution and optimization, mechanical filtration, UVGI, and humidity control are effective strategies for reducing the risk of dissemination of infectious aerosols in buildings and transportation environments.” The document goes on to posit that greater control of enhanced ventilation systems is key to fighting viral transmission. 

Finally, the American Public Transportation Association’s (APTA) June 2020 white paper, Cleaning and Disinfecting Transit Vehicles and Facilities During a Contagious Viral Pandemic, advises, “The CDC (Center for Disease Control) has stated that airborne transmission of the virus is more likely than transmission through surface contact … Adequate ventilation and air filtration of HVAC systems can reduce the likelihood of airborne exposure.”

While the quest for the perfect transit ventilation system is not new, an answer to the ventilation pandemic question plagues transit officials globally. But one system may have just found an answer through a technology originally designed for greater comfort and efficiency.

Looking for the “Air Necessities”

“This artificial intelligence (AI) platform reads the temperature, humidity, air quality and electricity consumption in metro stations in real time,” reports the Transports Metropolitans de Barcelona (TMB). “An algorithm combines this data with information such as the weather forecast and expected occupancy levels to predict environmental conditions at the stations and accordingly programs the operation of each fan to regulate temperature and energy consumption. Intelligent control of the ventilation will also bring the maximum amount of fresh air inside, which will increase hygiene and reduce the risk of proliferation of COVID-19 and various microorganisms.”

TMB Metro Director Ramon Bacardí adds, “This is a good example of the application of technologies for the benefit of improving the quality of service and with a direct effect on the customer’s travel experience. [It highlights] the contribution that the ventilation system can make to provide an environment of safety and comfort on the metro network [as operations resume following COVID-19 lockdowns].” 

One of the largest transit agencies in Europe, TMB manages an eight-line, 156-station metro network. And the AI platform TMB cites is called RESPIRA®. In July, TMB launched a pilot program to install RESPIRA® on its Metro Lines 1-5—lines that carry 94% of its ridership. If successful, the solution could be expanded to other large venues throughout Europe. So, what exactly is RESPIRA®? 

Created by SENER, a global engineering and technology group, RESPIRA® uses artificial intelligence and a dynamic algorithm to predict and control environmental conditions inside stations in real time. It takes into account everything from weather predictions to allergy forecasts to expected ridership levels and provides optimum operation based on targeted objectives or more general desired outcomes. Initially created to improve thermal comfort in stations, its robust AI could prove to be an effective, strategic tool in helping combat COVID-19. 

“The algorithm chooses the best overall environmental strategy taking every variable into account. Obviously, COVID-19 is the main concern right now,” explains SENER’s Guillem Peris-Sayol, a tunnel ventilation and fire-life-safety expert, university professor, and a RESPIRA® designer. “And we’re talking with the [Spanish] Ministry [of Science and Innovation] to finalize a ‘Sanitary Mode’ that addresses COVID-19 and other potential biohazards. RESPIRA® is proving to be a very effective tool already, but we’re testing sensors that detect other dangerous pathogens as well.”

RESPIRA® functions much like a brain that controls a metro’s entire ventilation system. Through sensors, RESPIRA® processes a vast array of data to give transit operators complete control of their system’s environment.

Peris-Sayol explains: “The metro is basically a duct where trains move the air. Add fans, users, lights, mechanical stairs, the ambient heat they give off, and many other factors (some with significant parameters) and you have a complex web of variables. We developed an algorithm to process this mountain of data instantly, giving complete control to operators. Traditionally, ventilation wasn’t easy to manage or control. But with the algorithm and sensors, you can focus on an entire metro system or zero in on one fan that’s malfunctioning. It provides tremendous flexibility and specificity. The algorithm processes all of the data from the sensors constantly and in real time and the AI component learns from it. And different modes give operators options to focus on one overriding objective, like air quality or cost or temperature. It’s even flexible enough to control for allergy season. 

“RESPIRA® was not originally designed for COVID-19, though again that’s the main concern right now. But it’s also a long-term investment for transit agencies, as it helps achieve sustainable goals, asset management, maintenance, etc. And it works equally well with both new systems and older, legacy transit systems. The algorithm combined with basic or smart sensors give any transit operator the power to control every aspect of their ventilation systems.” 

Peris-Sayol adds that on TMB, RESPIRA® will monitor and process more than 500 million datapoints a year. He also notes that its capabilities are not limited to transit, but can also be used for any complex space that contains many people including stadiums, shopping centers, and airports. That, too, is being explored by the Spanish science ministry.

Transit agency executives know that ridership is survival. Never has that been truer. And with the COVID-19 pandemic, transit executives must do everything in their power to bring back ridership to pre-pandemic levels. And one of the most important ways to do this is to ensure that from now on the air riders breathe is safe. For metro riders in Barcelona, that future is closer now.

Arthur Schurr is a New York-based writer who reports on transportation infrastructure.