Transport maps have become too complex for our brains to understand, according to science

The Tokyo subway map. Easy, right? Image: Tokyo Bureau of Transportation.

As you may have heard (from us, approximately weekly), London's Underground map might just need a redesign. Perhaps adding colours to DLR lines would simplify things. What if the Circle and District lines were shaped like a little penguin? Maybe stations in the suburbs could be more evenly spaced?

But a new study suggests that transport maps not only in London, but in other big cities like Paris, Tokyo and New York, could simply be too big and complex for our brains to easily process - which means no amount of mapping and re-mapping would help.

This idea is based on the fact that, just as researchers estimate that we can only maintain between 100 and 200 friendships at once (this is known as Dunbar's number) there might also be a limit on how much information we can handle while figuring out how to get from A to B. 

Researchers from a variety of institutions concluded in their wittily named paper, "Lost in transportation: Information measures and cognitive limits in multilayer navigation", that we can only deal with around 8 "bits" (i.e. binary, yes/no decisions) at once, and are unlikely to read a map with more than 250 connection points with much ease. In doing so, they're treating our brains a little like you'd treat a computer: figuring out how much processing it can do at once without overloading and crashing. Or, you know, tearing up the map and getting a taxi. 

Part of the issue is that most global cities are now multi-modal - they have subways, buses, trams and even cable cars. While subway maps alone may be simple enough to understand, once you include different modes on the same map, "more than 80 per cent of trips" in New York, Paris and Tokyo are above the 8-bit limit. 

This slightly confusing graph shows that the maps featuring only subway systems (the dotted lines) mostly feature trips under the limit, while most trips on multi-modal maps (the solid lines) go over:


As a result, the researchers recommend maps which separate out layers so users can more easily understand them:

...traditional maps that represent all existing bus routes have a very limited utility. This result thus calls for a user-friendly way to present and use bus routes. For example, unwiring some bus-bus connections lowers the information and leads to the idea that a design centred around the metro layer could be efficient. However, further work is needed to reach an efficient, “optimal” design from a user’s perspective.

One example of better map design cited by the researchers are London's "spider bus maps", displayed in bus stops across the capital (you may have squinted at one in the early hours last time you got a night bus with a dead phone). They map out all bus routes proceeding from your current location, so you only see information relevant for your journey, plus they zoom in on the roads around the bus stop. Here's one for Harringay in northwest London:

Click to expand. Image: Transport For London.

This, however, doesn't help you much with longer journeys, or ones involving the Tube. The reality is that most trips in big cities require a combination of modes, especially if you're hoping to use the fastest route possible. As a result, the researchers say that transport in cities has simply become too complicated for our brains to handle on a single map: 

Human cognitive capacity is limited, and cities and their transportation networks have grown to a point that they have reached a level of complexity that is beyond humans’ processing capability to navigate in them. 

Even the attempt to map tangled city networks at all can seem futile, which is why the growth of transport apps and route planning websites is so crucial:

 Indeed, the growth of transportation systems has yielded networks that are so entangled with each other and so complicated that a visual representation on a map becomes too complex and ultimately useless...

The information-technology tools provided by companies and transportation agencies to help people navigate in transportation systems will soon become necessary in all large cities. 

So there you have it: using Citymapper doesn't mean you're lazy. It's just a necessary supplement to your cognitive processing power.  


How collecting food waste could slow climate change – and save us money

Cleaning up. Image: Getty.

Food waste is a global problem, and one that’s driving climate change. Here in the UK, the country’s biodegradable waste goes to a landfill, where it breaks down to produce methane, a gas that is roughly 30 times as bad as carbon dioxide.

And yet there’s a simple solution. With the exception of garden waste, which often contains lignin from woody matter, all biodegradable materials, including much of our food waste, could instead be processed in anaerobic digesters. This decomposition in an atmosphere devoid of oxygen produces biogas, which can then be used to generate heat and electricity.

This is more or less the same process that takes place in landfill sites, except that the biogas can’t escape from an anaerobic digester as it can from landfill – meaning the breakdown of the organic matter takes place in an environment that is enclosed and controlled.

The result is biogas consisting of 60 per cent methane and 40 per cent carbon dioxide, which can be burnt in order to generate heat or used as a fuel for vehicles. It could also be used to generate electricity after the biogas has been scrubbed, which can then either power the anaerobic digester or be exported to the national grid. The process also produces digestate, a solid and liquid residue that can be returned to farmland as a soil conditioner. The amount of biogas and the quality of digestate varies according to what feedstock is used in the digester.

This process is already widely used both across Europe – particularly in Denmark, Sweden, Germany and Austria – and elsewhere globally, particularly in India and Thailand. What's more, this move towards separate food waste collection is already happening in countries outside the UK, and its momentum is increasing according to the World Biogas Association. Already, major cities, including New York, Paris, Oslo, Copenhagen, Auckland, San Francisco, Mexico City and many others are regularly collecting food waste from their citizens. The decisions to do so are usually taken at city level, but enabling legislation from national governments assist in this.

At present the UK is lagging behind. Only 109 local authorities in England, about 33 per cent of the total number, collect food waste as of May 2018, according to the Anaerobic Digestion and Bioresources Association (ADBA). Yet making a separate food waste collection mandatory across the UK and running the food waste through anaerobic digesters, could supply enough biogas to generate 36 per cent of UK electricity, according to a 2007 Friends of the Earth report. This percentage could be increased again if food waste from restaurants, cafeteria and retailers was also collected. 

ADBA’s research also suggests that universal separate household food waste collections would trigger the construction of around 80 new anaerobic digester plants for food waste processing. This would add an extra 187 megawatts equivalent (MWe) of capacity, powering 285,000 extra homes – representing all the homes in a city the size of Glasgow. Data from WRAP suggests that further food waste collection from businesses would add around a further 10 per cent, depending on the quality of the feedstock collected and what exemptions were applied (for example, it might only apply to businesses collecting more than 50 kilograms per week or the lower threshold of 5kg).

A 38 per cent improvement in food waste collection from flats in Ealing alone could generate £26,000 of annual savings for the London borough, £28,000 in revenue for a local anaerobic digester (based on electricity sales to the national grid) and reductions in carbon dioxide emissions of around 270 tonnes, found Londoners Lab, a collaborative project consisting of Greater London Authority, University College London, Ferrovial Services Centre of Excellence for Cities and Future Cities Catapult.

ADBA has been campaigning on this issue for a while, but the good news is that the government finally signalled its intention to introduce separate food waste collections in its forthcoming Resources & Waste Strategy, which will ensure that all homes and suitable businesses in England will have access to food waste collections by 2023. The next step, following the government announcement, is a consultation, but it is widely acknowledged that additional funding would be needed by local authorities to achieve this, as the business case isn’t currently strong enough.