Best Practices in the Sterilization of Mass Transit Property.

“We all are staring at an unprecedented time wherein the recent pandemic has brought the world to a halt. The safety of the population has become the top priority of the governments across the globe and reactive versus pro-active approach is the way forward to contain the COVID 19 virus”


Overview: The Biggest challenge for the Mass Transportation organizations and bus companies, as well as rideshare businesses and airlines, etc. staring at them is gaining the passengers confidence to resume travel. There are significant challenges as there is no “Post Covid Situation ‘in sight. The virus remains active while Scientists are on the job to find the cure. We all are staring at an unprecedented time wherein the recent pandemic has brought the world to a halt. The safety of the population has become the top priority of the governments across the globe and reactive versus pro-active approach is the way forward to contain the COVID 19 virus. At this point, it’s common knowledge that the COVID-19 virus is spread through person-to-person contact. But there is also compelling evidence that suggests the virus can remain active for hours  ̶  even days  ̶  on some types of surfaces. And this problem, especially for the transit industry.   The New England Journal of Medicine just released a report that investigated claims – “how long the virus can remain viable on different kinds of “surfaces”

Their analysis revealed that COVID-19:“Was more stable on plastic and stainless steel than on copper or card board “The fact that COVID-19 is so virulent makes the cleaning and disinfecting (of course the difference between cleaning and “disinfecting” has to be understood) of every mode of transport  ̶ 

  • be it train
  • plane
  • Bus
  • Taxi
  • Or subway, etc.

Contact mapping mass transit:

  • According to current evidence, COVID-19 virus is primarily transmitted between people through respiratory droplets and contact routes.In an analysis of 75,465 COVID-19 cases in China, airborne transmission was not reported. The mass transit system with huge SS interiors has high exposure to the virus –  Coronavirus can survive for two to three days on plastic and stainless steel surfaces
  • “The virus that causes COVID-19 remains for several hours to days on surfaces and in aerosols, a new study published in the New England Journal of Medicine found” Cleaning versus disinfecting is the answer. 
  • The study suggests that people may acquire the coronavirus through the air and after touching contaminated objects. “Scientists discovered the virus is detectable for up to three hours in aerosols, up to four hours on copper, up to 24 hours on cardboard and up to two to three days on plastic and stainless steel”

Note: Steel feels clean. After all, hospitals and labs use plenty of stainless steel surfaces in operating rooms and other sterile areas. However, when it comes to coronavirus, it may not be as safe as you think.

Measuring Methodology – How they measured it”

  • Scientists measured this by laying down a few drops of fluid containing COVID-19 viral particles.
  • They then collected samples at regular time points to measure how many viruses were still present on the stainless steel surface.
  • They compared this to other surfaces including plastic and cardboard.

By doing so, they were able to generate the model below:

 Steel  – COVID-19 decay

% Virus Alive                          Time in hours

100%                                                     0h

80%                                                        5h

60%                                                        10h        

40%                                                        15h        

20%                                                        20h

  • As evident in the data above, COVID-19 corona viruses can live quite a long time on a stainless-steel surface.
  • While most corona viruses die quickly, some can live on but on steel it potentially remains infectious, for over a day.

Contact Audit / Mapping:

An important part of any program designed to fight the virus is to conduct a “contact audit or mapping” And, while it’s true that the passengers are more likely to be infected by coming into contact with a contaminated surface, it’s worth noting that “80% of bacteria are transmitted by hands which may touch the surface within the subway / planes / trains etc and 76 out of 100 people either don’t wash their hands at all or don’t use soap2.”

It should come as no surprise then that New York’s Metropolitan Transportation Authority (MTA) announced3 that all of its trains, buses, and other modes of public transports will be sanitized every 72 hours. Plus, they are going to disinfect often-touched surfaces in stations every day. San Francisco’s Bay Area Rapid Transit (BART) system also intends to implement similar practices on its vehicles and in stations and bus terminals. 

A Daily Sterilization Checklist a must

We say a ‘daily’ checklist because it is often impractical to clean often-used vehicles more than once a day, even if you have reduced ridership. It takes about three hours to completely clean a city bus, according to the MTA. But they have 1,000 buses on the roads  ̶  to say nothing of their immense subway system and suburban rail services  ̶  so you can immediately see how daunting a task this can be.

Still, it has to be done, one way or another.

As such, transportation organizations and bus companies, as well as ride-share businesses and airlines, etc, need to have ‘to-do’ checklists in place so that every single cleaning assignment can be tracked and proper records kept. Among the tasks a company or organization should accomplish:

1.  Disinfecting surfaces (not cleaning) and objects that are often touched.  

  • On trains you should see to doors, handrails, seat head rests, seats themselves, floors, and windows; plus, in the bathrooms, doorknobs, lights switches, sink handles, toilets, toilet handles, mirrors, sinks and soap dispensers.
  • On planes, the same objects should be cleaned, as well as carpeting, headphone sets, tray tables, over-head compartments, etc.
  • On buses, ceilings, windows, window ledges, walls and floors should be wiped down with cleaning agents and disinfectants. Upholstered seats should be vacuumed, and damaged seats replaced. You should include stanchions, entry/exit-way grab rails, pull cords stop buttons, the top of the fare box and the driver’s area.

Getting Your Staff on Board

 Organizations and transport operators companies having their own, dedicated cleaning staff or an outside firm that offers the service on a contract basis will come into effect to clean the mass transit. A word of caution “is it disinfecting?? Or is it cleaning!! A question to be asked and thoroughly deliberated “Cleaning cannot be categorized as disinfecting

For operations that cannot justify the cost of such guaranteed assistance, the onus falls on them to bring the same level of cleanliness and hygiene to their operations. And by the way, this isn’t just a purely desirable goal. It’s a business imperative! Not being conscientious and committed to a thorough “disinfection” regimen can be a recipe for disaster! The reputation you spent years building can disappear overnight if your vehicles become known for their lack of hygiene, or, to put it bluntly, being downright infectious.

Options for Operators

Many products are available for decontamination of these critical spaces. There are differences in product effectiveness, cost, potential residual damage and operational limitations. Two particular methods, presented below, are being employed to reduce or eradicate hazardous microorganisms and viruses-

A. Biocidal Properties of Hydrogen Peroxide Vapor ( HPV) based Equipment’s

Hydrogen peroxide Vapor (HPV) is one of the effective way to sterilize and disinfect surfaces that are contaminated with undesirable microorganisms. The United States Environmental Protection Agency (EPA) classifies HPV as a disinfectant by virtue of its biocidal and pesticidal properties.

Sterilizing with HPV involves release of a known concentration of vaporized hydrogen peroxide throughout an enclosed space, such as a lab. This is typically achieved with a HPV generator. These generators first remove moisture from ambient air and then pass liquid hydrogen peroxide past a vaporization module to produce a concentrated gaseous form of the chemical.

The biocidal mechanism of action for hydrogen peroxide is attributed to chemical oxidation of cellular components. This oxidation rapidly interrupts vital chemical processes vital to microbial survival, and thus sterilizes the environment. For these reasons, HPV is used in many applications when personnel seek to disinfect environments contaminated by virulent microbes.

Various manufactures producing range of manual and IR based auto navigation robotic systems which are capable of spraying HPV at desired rate with very small droplet size as good as less than 10 microns which helps to dry the surfaces very fast and no strains on surfaces.

B. Shining a Ultra-violet light on Microorganisms (UV-C ) based Equipment’s

Ultraviolet germicidal irradiation has been a mainstay for killing and inactivating microorganisms for well over a century. This process utilizes short-wavelength ultra-violet C light to kill microbes. UV-C light encompasses a range of 100 to 280 nm, but the most effective wavelength for decontamination is between 250-260 nm.

Exposure to the light inactivates microbial genomic DNA. UV-C light creates lesions called thymine dimers, which cannot be resolved by cellular-DNA repair mechanisms. This injury to cellular DNA impairs vital cellular functions and ultimately leads to the death of the microorganism. Thus, ultraviolet germicidal irradiation can be an effective means of sterilizing surfaces, instrumentation and facilities

Which is better on what surface?

UV germicidal irradiation is only effective in sterilizing surfaces that are in the rays’ line of sight. Any portion of a surface that is “hidden” by other objects will not be exposed, and therefore not sterilized.

Operator safety is one obvious concern when using UV-C based decontamination systems. In the same way that UV-C light damages microbial DNA, irradiation can also cause DNA damage in humans. Thus, procedures need to include instructions for keeping personnel at a safe distance from these light sources.

As ultraviolet (UV) radiation consists of photons with high energy relative to visible light, it can cause degradation in the form of physical and chemical changes in susceptible materials.

HPV is arguably the most effective form of surface and facility decontamination, however quite hazardous to personnel. Therefore, carefully calculate and document two important factors: the concentration of hydrogen peroxide used during cycles, and the time allowed for these vapors to disperse.

How to overcome this various material surfaces challenge:

Withthis formula and some experiments one can find out the amount of time required for complete disinfection of target surface and it can be verified with UVC photosensitive paper dosimeters-

UVC- Photodegradation of Materials

The UV-C light can be detrimental to organic materials. If vulnerable materials are not shielded, substantial degradation can occur.

These damages are observed only after days or weeks of exposure at irradiances > 1 mW/cm2

For lower irradiances, very long exposure time (months) are required to damage materials.

Some common polymers such as PE show signs of degradation at UV doses (10-100 J/cm2) that are several hundred or even thousand time higher than those required to inactivate microorganisms

Thus, It can be concluded that with limited time applications such as the case of UV-C sanitizers, the material photodegradation is not that critical.

Comparison between UV-C and HPV

Process TimeLessMore
Biocidal TargetsFewerGreater
Decontamination reachexposed surface onlyall surfaces
Safety Concernvisual exposureaerosol exposure
Measurement of efficacyTo ensure targeted areas are covered must be measured and reconfirmed sufficient dosage of UV-C is delivered and the target surfaces are fully disinfectedVery difficult to measure the disinfection level

Human Cleaning versus robotic cleaning

In the rush to clean and disinfect vehicles, there’s a better than even chance that some folks will forget  ̶  and in certain cases, ignore  ̶  some transportation facilities, such as bus and trains, waiting rooms, ticketing areas, and the conveniences they offer: Public seating, toilets and bathrooms, on-site retail stores, fast-food outlets (e.g. McDonald’s, Starbucks, Pizza Hut, Dunkin Donuts, etc.), gift shops, elevators and escalators and so on.

The problem: Any one these facilities can become a COVID-19 hotspot.

For example, New York’s Penn Station handles some 650,000 passengers every day, while the MTA provides subway services for 5,437,587 riders operating out of 472 stations. And practically everything in their facilities  ̶  including stations and high-touch surfaces such as turnstiles, ticket machines, handrails, and so forth — have to be thoroughly disinfected  at least once a day, more if possible.  

The reactions to the COVID-19 pandemic and its effects on societies and economies around the world cannot be understated. Although scientists have warned of fast-spreading diseases, most governments were underprepared, and companies of all sizes are asking employees to telecommute or are facing shutdowns .

The novel coronavirus has increased interest in robots, drones, and artificial intelligence, even as some testing of autonomous vehicles pauses on public roads. These technologies can help deal with massive staffing shortages in healthcare, manufacturing, and supply chains; the need for “social distancing;” and diagnosis and treatment. We don’t yet know the long-term effects, but here are more examples of how robotics is addressing the challenges posed by the pandemic.

MTR Corp., the Hong Kong subway system, is using vaporized hydrogen peroxide (VHP) robots developed with Avalon Biomedical (Management) Ltd. to disinfect rail cars.

“With a global pandemic quickly on the rise, government officials will need to act quickly in search of a scalable solution that will help slow down the spread of coronavirus,”


“Mass Transit is a critical component of the mobility ecosystem of all large cities, so as cities begin to cautiously re – open , encouraging passengers back will require that organization ensure rider safety and increased confidence is using the transit “

There are and will be many lessons to draw from the COVID-19 pandemic affecting public transit agencies. Looking inward at responses and outward at system actions in service

Public transit agencies will need to determine how best to prepare for and respond to various post-peak scenarios, ranging from complete virus eradication to an endemic situation with a low level of community transmission. This “new-norm” is completely uncharted territory and will require cooperation and collective action, including creating a Contagious Virus Response Plan, stockpiling and investing in solutions, technological or other, to offer more resilient to future disruptions.

Like flattening the curve, together, we can build back a resilient public transit sector that is vibrant and fit for the post-COVID-19 world.

Note : Author could reached at the following mail ids towards further questions or cost benefit analysis

  1. [email protected]
  2. [email protected]
  3. [email protected]


  • Neeltje van Doremalen, Trenton Bushmaker, Dylan H. Morris, Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1, New England Journal of Medicine, March 2020.
  • ibid.
  • MTA Issues Agency-Wide Update on Precautionary Measures Against Coronavirus, MTA Press Releases, March 2020.
  • Disinfectants for Use Against SARS-CoV-2, Pesticide Registration, Environmental Protection Agency, March 2020.
  • Richard E. Fairfax, OSHA’s policy regarding the use of EPA-registered disinfectant, Standard Interpretations, Occupational Safety and Health Administration, February 2005.
  • Introduction to Subway Ridership, Metropolitan Transportation Authority, 2020.
  • Report by Terra Universal.
Daily Updates from Metro & Railway


  1. This article is discussing sanitizing, not sterilizing. The difference is that sterilizing eliminates 100% of the germs. Sanitizing greatly eliminates germs, perhaps 99.9%, but does not eliminate all germs.

    It is not practical to sterilize vehicles. But sanitizing is feasible.


Please enter your comment!
Please enter your name here

This site uses Akismet to reduce spam. Learn how your comment data is processed.