Why doesn’t the tube make handpoles out of self-sterilising metals? And what is grippage?

Why don't these kill germs? The interior of an ageing Circle line train in 2010. Image: Maurits90/Wikimedia Commons.

In February 2015, bacteriologists from Cornell University published their results after spending more than a year swabbing New York City’s Subway trains and stations for bacteria. The results sounded icky: not only are there hundreds of different microbial species living throughout NYC’s transit system, on the poles and seats and turnstiles that humans touch every day, but half of them were completely unfamiliar to science. Anthrax and the bubonic plague were among those bacteria which were recognised.

Of course, the fact that New Yorkers aren’t dying off like 14th century Europeans implies that the dirtiness (or, rather, perceived dirtiness) of the subway isn’t a pressing public health issue. The study authors were keen to point out that commuters shouldn’t overreact to the news.

The same will apply to London, both in terms of the microbes living throughout the Underground and in the near-non-existent risk they pose to travellers. Yet as I was sat on one of Transport for London’s new S Stock trains on the Hammersmith & City line last week, fully aware of the first signs of a cold in my nose and my throat, my thoughts drifted to that study.

TfL likes to colour-code its lines so that the interior decor of the trains matches the lines they run on (so orange on the Overground, blue on the Piccadilly, etc.). These new trains are running on the Metropolitan (purple), District (green), Hammersmith & City (pink) and Circle (yellow) lines – yet all are decked out in bright, garish yellow. God knows what’s living on those neon poles and handstraps that keep passengers from falling down.

We know that public transport is a vector for disease transmission, especially when it comes to seasonally-influenced illnesses like the flu. We also know that there are materials which self-sterilise – that is, they’re highly toxic for any single-cell organisms that are unfortunate enough to land on them. This “oligodynamic effect” was first discovered in 1893, and lots of different metals – from silver to aluminium, lead to copper – possess it.

So the question is: why aren’t the hand poles in Underground cars and on buses made of antimicrobial metal?


A Santiago metro station, complete with bacteria-killing handrails. Image: AntiMicrobialCopper.com.

In some parts of the world, the answer is actually “they are”. The subway system in the Chilean capital Santiago, for example, uses antimicrobial brass handrails, which were installed in 2011 as part of a wider healthcare campaign. But this is an exception, not a rule.

Jean-Yves Maillard is a pharmaceutical microbiologist from the Cardiff University who researches the use of antimicrobial materials in hospitals, and specifically the two most promising metals: silver and copper (or alloys of copper, rather). It turns out that these things kill germs best when “humidity is 100 per cent, so they are underwater – and that’s not how these surfaces exist on the metro, or Tube, or buses.”

Instead, to get a better idea of how well they work, he’s tested them when they’re dry (which means between 30 and 40 per cent humidity, which is typical for the UK), and when they have “droplets” (i.e. someone’s sneezed) on them.

The results are still impressive: within 30 minutes of contact with the most effective copper alloys, 99.99 per cent of Staphylococcus aureus bacteria – a bug responsible for everything from skin infections to respiratory diseases, and including the infamous antibiotic-resistant MRSA strain – were exterminated in the droplet test, while the dry test still saw around a 90 per cent reduction.

“When it's very dry – the worst case scenario, a very dry summer and so on, above 20 degrees – you'd get something like 99.99 per cent reductions within 30 minutes,” he said. “If someone sneezes, then after 30 minutes on that surface the bacteria is likely to be killed. I imagine for some viruses it would be the same as well. [But] if you haven't got droplets, then that activity really drops sharply. You'll get at most 90 per cent reductions, but probably less than 90 per cent, within 30 minutes. You'll kill some, but not all.” Silver was less effective in the droplet test, and not effective at all in the dry one.

This might make switching to copper-based antimicrobial subway and bus poles seem like an easy win that TfL missed when ordering its newest trains. But Maillard is keen to stress that there are some important downsides.

It rhymes with "fromage"

Firstly, if a surface is cleaned relatively frequently, then the extra cost from using more expensive materials might be more than those of simply paying for someone to wipe everything down a bit more frequently each day, for the same result. And these surfaces are no substitute for cleaning – Maillard emphasises that antimicrobial surfaces work “in addition” to cleaning, not as a replacement. And, when I contacted TfL, health & safety director Jill Collis made it clear that they clean the network “throughout the day and night” already.

The second reason is appearance. According to Collis, “the handrails in carriages are designed to be easy to see, meet safety standards and be suitable for daily use by millions of customers”. (I also discovered that the internal TfL term for the things that passengers hold onto isn’t “handrails”, but “grippage” – pronounced to rhyme with “fromage”.)

This is an important point – and TfL also said that, in accordance with the Vehicle Accessibility Regulations Act 2010, “any passenger handrail fitted in or to a rail vehicle must … contrast with the parts of the rail vehicle adjacent to that handrail”.

In other words, the bright colours on the Tube are primarily so that the visually-impaired are better able to see them. While the brass handrails of the Santiago subway may look somewhat classy, they also blend into the background in dark, underground spaces.

A third important issue is value for money. The handrails on the Tube are made of aluminium, which has a good ratio of weight to cost to strength; copper and silver, less so. “In hospitals, the debate is all about costs,” Maillard said. “[Surfaces] maybe get cleaned once a day, and with copper surfaces there are indications that at the end of the day the [the microbial burden] will be less than normal metal surfaces. That's the interest in it. But the big question is, is it cost effective?”

Then there’s even a fourth issue, most relevant to silver, which is that it perversely seems to make drug-resistant superbugs more likely. Making subway poles out of solid silver is, clearly, ridiculous, but it’s common for nano-particles of silver to be placed within other material to give it some antimicrobial properties – not as good as copper alloys, of course, but still something.

Maillard points to a January 2015 report from the EU Commission’s Scientific Committee on Emerging and Newly Identified Health Risks (Scenihr) into the possible dangers posed by the use of nano-silver in medical and consumer devices. It found that research is “urgently needed” into the possible toxic effects of long-term exposure to silver in consumer products, and also that the genetic adaptation of bacteria to silver could increase resistance.

“What you will find is that now you have a huge amount of surfaces that contain antimicrobials,” Maillard explained. “Lots of plastics, washing machines, photocopiers, in pens, televisions, television remote controls – most of them contain silver or nano-silver, because they don't affect the colour. The concentration that they use is very low, there are question marks over its efficacy, and questions about whether it's going to promote resistance of those organisms with those products.”

So, put it all together and it doesn’t look good for Tube poles that clean themselves. Copper alloys work best, but would have to be painted to comply with health & safety legislation, defeating the purpose. And, while it’s possible to stick silver particles into the paint as an alternative, it’s not very good, especially when the extra cost is factored in – and that’s without considering make it more likely that truly nasty bacteria can thrive and evolve on public transport.

Best stick to hand sanitising gel. Much easier.

Want more of this stuff? Follow CityMetric on Twitter or Facebook


In a world of autonomous vehicles, we’ll still need walking and cycling routes

A Surrey cycle path, 1936 style. Image: Getty.

The CEO of Sustrans on the limits of technology.

We are on the cusp of dramatic changes in the way we own, use and power our means of transportation. The mobility revolution is shifting from an “if” to a “where” and when”.

There are two different futures currently being imagined. First up, a heaven, of easy mobility as portrayed by autonomous vehicle (AV) manufacturers, with shared-use AV freeing up road space for public spaces and accidents reduced to near zero. Or alternatively, a hellish, dystopian pod-world, with single-occupancy pod-armadas leading to an irresistible demand for more roads, and with people cloistered away in walkways and tunnels; Bladerunner but with added trees.

Most likely, the reality will turn out to be somewhere in between, as cities and regions across the globe shape and accommodate innovation and experimentation.

But in the understandable rush for the benefits of automation we need to start with the end in mind. What type of places do we want to live in? How do we want to relate to each other? How do we want to be?

At Sustrans we want to see a society where the way we travel creates healthier places and happier lives for everyone – because without concerted effort we are going to end up with an unequal and inequitable distribution of the benefits and disbenefits from the mobility revolution. Fundamentally this is about space and power. The age-old question of who has access to space and how. And power tends to win.  

The wealthy will use AV’s and EV’s first – they already are – and the young and upwardly mobile will embrace micro mobility. But low-income, older and disabled residents could be left in the margins with old tech, no tech and no space.

We were founded in 1977, when off the back of the oil crises a group of engineers and radical thinkers pioneered the transformation of old railway lines into paths that everyone could walk and cycle on: old tech put to the service of even older tech. Back then the petrol-powered car was the future. Over 40 years on, the 16,575-mile National Cycle Network spans the length and breadth of the UK, crossing and connecting towns, cities and countryside, with over half of the population living within two miles of its routes.

Last year, more than 800 million trips were made on the Network. That’s almost half as many journeys made on the rail network, or 12 journeys for every person in the UK. These trips benefited the UK economy by £88m through reduced road congestion and contributed £2.5bn to local economies through leisure and tourism. Walking and cycling on the Network also prevented 630 early deaths and averted nearly 8,000 serious long-term health conditions.

These benefits would be much higher if the paths on the entire Network were separated from motor traffic; currently only one third of them are. Completing an entirely traffic-free walking and cycling network won’t be simple. So why do it?

In a world of micro-mobility, AVs and other disruptive technology, is the National Cycle Network still relevant?

Yes, absolutely. This is about more than just connecting places and enabling people to travel without a car. These paths connect people to one other. In times when almost a fifth of the UK population say they are always or often lonely, these paths are a vital asset. They provide free space for everyone to move around, to be, and spend time together. It’s the kind of space that keeps our country more human and humane.

No matter how clever the technological interface between autonomous vehicles and people, we will need dedicated space for the public to move under their own power, to walk and cycle, away from vehicles. As a civil society we will need to fight for this.

And for this reason, the creation of vehicle-free space – a network of walking and cycling paths for everyone is as important, and as radical, as it was 40-years ago.

Xavier Brice is CEO of the walking and cycling charity Sustrans. He spoke at the MOVE 2019 conference last week.