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.  


Here’s how we plant 2 billion more trees in the UK

A tree in Northallerton, North Yorkshire. Image: Getty.

The UK’s official climate advisor, the Committee on Climate Change (CCC), recently published a report outlining how to reduce the 12 per cent of greenhouse gas emissions that come from land use by two thirds by 2050. Alongside recommending cutting meat and dairy consumption by 20 per cent, the report calls for the annual creation of up to 50,000 hectares of broadleaf and conifer woodland for the next three decades. This would increase forest cover from 13 per cent to at least 17 per cent – a level not seen in Britain since before the Norman invasion.

Reforestation at that rate would mean creating roughly the area of the city of Leeds every year for the next three decades. At typical stocking densities of 1,500 stems per hectare, the ambition is to establish some 2.25 billion additional trees. Given that the UK, as with most of Europe, is in the grip of ash dieback, a disease likely to prove fatal for many millions of native ash trees, the scale of the challenge is massive.

On a crowded and intensively farmed island like Britain, unlocking a million and a half hectares of land will be no mean feat. But it’s not impossible – and is an unprecedented opportunity not only to tackle the climate crisis but also the biodiversity crisis that is every bit as detrimental to our wellbeing.

Trees and farms

One million and a half hectares is just 6 per cent of the mainland UK’s land area. To give some sense of perspective on this, 696,000 hectares of “temporary grassland” were registered in 2019. So if land supply is not the problem, what is? Often it’s cultural inertia. Farmers are firmly rooted to the land and perhaps understandably reluctant to stop producing food and instead become foresters. But the choice need not be so binary.

The intensification of agriculture has caused catastrophic declines in many species throughout the UK by reducing vast wooded areas and thousands of miles of hedgerows to small pockets of vegetation, isolating populations and making them more vulnerable to extinction.

Integrating trees with the farmed landscape delivers multiple benefits for farms and the environment. Reforestation doesn’t have to mean a return to the ecologically and culturally inappropriate single-species blocks of non-native conifers, which were planted en masse in the 1970s and 1980s. Incentivised under tax breaks to secure a domestic timber supply, many of the resulting plantations were located in places difficult or in some cases impossible to actually harvest.

Productive farmland needn’t be converted to woodland. Instead, that 4 per cent of land could be found by scattering trees more widely. After all, more trees on farmland is good for business. They prevent soil erosion and the run-off of pollutants, provide shade and shelter for livestock, a useful source of renewable fuel and year-round forage for pollinating insects.

The first tranche of tree planting could involve new hedgerows full of large trees, preferably with wide headlands of permanently untilled soils, providing further wildlife refuge.

Natural regeneration

Where appropriate, new woody habitats can be created simply by stopping how the land is currently used, such as by removing livestock. This process can be helped by scattering seeds in areas where seed sources are low. But patience is a virtue. If people can learn to tolerate less clipped and manicured landscapes, nature can run its own course.

A focus on deliberate tree planting also raises uncomfortable truths. Most trees are planted with an accompanying stake to keep them upright and a plastic shelter that protects the sapling from grazing damage. All too often, these shelters aren’t retrieved. Left to the elements, they break down into ever smaller pieces, and can be swept into rivers and eventually the ocean, where they threaten marine wildlife. Two billion tree shelters is a lot of plastic.

The main reason for using tree shelters at all is because the deer population in the UK is so high that in many places, it is all but impossible to establish new trees. This also has serious implications for existing woodland, which is prevented from naturally regenerating. In time, these trees will age and die, threatening the loss of the woodland itself. Climate change, pests and pathogens and the lack of a coordinated, centrally supported approach to deer management means the outlook for the UK’s existing treescape is uncertain at best.

An ecologically joined-up solution would be to reintroduce the natural predators of deer, such as lynx, wolves, and bears. Whether rewilding should get that far in the UK is still the subject of debate. Before that, perhaps the focus should be on providing the necessary habitat, rich in native trees.

A positive response would be to implement the balanced recommendations, made almost a decade ago in a government review, of creating more new habitat, improving what’s already there, and finding ways to link it together. Bigger, better, and more connected habitats.

But the UK is losing trees at increasing rates and not just through diseases. The recent removal of Victorian-era street trees in Sheffield and many other towns and cities is another issue to contend with. As the climate warms, increasing urban temperatures will mean cities need shade from street trees more than ever.

Trees aren’t the environmental panacea that the politicians might have people believe – even if they do make for great photo opportunities – but we do need more of them. Efforts to expand tree cover are underway across the world and the UK will benefit from contributing its share. Hitting the right balance – some commercial forestry, lots of new native woodland and millions of scattered trees – will be key to maximising the benefits they bring.

Nick Atkinson, Senior Lecturer in Ecology & Conservation, Nottingham Trent University.

This article is republished from The Conversation under a Creative Commons license. Read the original article.