Speed vs coverage: How do metro systems decide how to space their stops?

The Paris Metro: quite close to another station, this. Image: Getty.

The Paris Metro averages a stop every 600m. The Moscow Metro averages a stop every 1.7km. Most of the world's largest systems are in between, several clustering in the 1.2-1.3 km range, including the London Underground, the Tokyo subway, and the Mexico City Metro.

But why is this? How come metro builders in some cities chose to build stations three times as far apart as in others? And what about those cities that have no metro system, but are building one, such as Tel Aviv or Sydney? What should they do?

The basic tradeoff here is between speed and coverage. Wider stop spacing means fewer locations have a metro station, but the speed between the stations is higher. The Moscow Metro averages 41 km/h, while the Paris Metro only averages about 25km/h. Other systems are intermediate: in Tokyo the average speed is about 30km/h; in London 33km/h.

There are other factors determining average speed, so that newer lines are often fast for their stop spacing. But each additional station adds about 40-60 seconds of travel time, depending on top speed, track quality, and train acceleration capabilities. The tradeoff, then, is the question: are more stations worth the extra travel time?

Each metro-building tradition answers this question differently. In cities where the metro extends deep into suburbia, stop spacing is wide; Paris built the RER as a separate system, with express stop pattern, because the Metro was too slow to effectively serve the suburbs.

Moreover, different countries make different decisions based purely on tradition. Under Parisian influence, the Montreal and Lyon Metros have short stop spacing; under Moscow's influence the metro systems in the former Communist Bloc, from Eastern Europe to China and North Korea, usually average more than 1.5 km between stations. With neither influence, cities in developing countries that build new metros, such as in South Asia, seem to use the same stop spacing as London or Tokyo.

But there is more to the stop spacing decision than the speed versus coverage tradeoff. Large cities, which expect to build many metro lines, need to plan how those lines will intersect in their cores. The San Francisco urbanist Brian Stokle wrote about the related subject of line spacing: how cities space parallel metro lines in their central business districts. Using American examples, Stokle argues that the typical space for parallel lines is 500-700 meters; this also appears to be the average in Paris and in central London.

The upshot is that if two lines are parallel, spaced about half a kilometer apart, then a line that intersects them orthogonally had better have two stops half a kilometer apart, for transfers. For example, in the diagram below the red and blue lines are roughly parallel, and the black line is orthogonal to them.

This looks familiar. Image: author provided.

Metro planners aim to provide a transfer station at the intersection of every pair of lines. In practice, because most metro systems have denser line spacing than stop spacing, this is not always feasible. Metro systems that feed geographically small central business districts, such as central London or central Tokyo, end up with multiple missed connections; New York, where the subway was built by three separate companies, has more than twenty missed connections. But usually, there is only a small handful of missed connections, often just one or two.

A separate question is that of express lines. In New York, five of the nine subway trunk lines have four tracks, with local and express trains; in Seoul, Line 1 has four tracks as well. Thanks to the express lines, New York maintains very narrow stop spacing on the local lines.


But a more common situation is one in which every metro line has two tracks, with all trains making all stops, on which some lines are more express than others. In Paris, the RER A was built as an express version of Metro Line 1, and, decades later, Metro Line 14 was built with longer stop spacing as well, to relieve the central segment of the RER A.

This situation leads to missed connections. The RER A tries to make connections when it can, but still crosses a few lines without a transfer, or else it would be hardly any faster than Line 1.

London's equivalent, Crossrail, does the same: it misses some connections to north-south lines, because if it didn't, it wouldn't be faster than the Central line, simply because line spacing in Central London is so dense. Within the Paris Metro, excluding the RER, there are three missed connections, two involving Line 14; an under-construction extension of Line 14 misses yet another connection. In Asia, several cities, including Hong Kong, Beijing, and Delhi have express lines to the airport, with missed connections in every case.

But it's easier to build networks with long stop spacing in newer cities, purely because of how their business districts are laid out. In old industrialised cities like London, Paris, New York, and even Tokyo, there is a dominant CBD, a few square kilometers in area, and most metro lines enter it. In all of these cities, the CBDs for the most part predate the metro system.

In newer cities in developing countries, the CBDs look different, with multiple centers, sometimes purpose-built. This leads to longer line spacing, matching the wide stop spacing. On same-scale maps of their networks, Paris, London, and Tokyo all look like hard-to-follow blobs in their centers, whereas Chinese cities, especially Beijing, still look clear. In Beijing, the only missed connection today involves the airport express line.

The most ideal metro network looks radial, with a circular line or two. Every pair of radial lines should intersect, once, with a transfer station, and every radial should intersect every circle twice, again with transfers. Ideally interchange stations should only involve two lines at a time, to avoid clogging the most popular locations. The diagram above is a good example of a coherent network with three lines. Unfortunately, the interaction of line spacing and stop spacing makes the ideal network difficult to construct. It's also unlikely that the street network is perfectly aligned for this; for example, cities with street grids, like Beijing or Philadelphia, can't easily build lines diagonally to the grid.

 

The ideal network? At least, if you ignore the chaos of that central station. Image: CityMetric.

This means that the only way to guarantee easy connections between metro lines in most large cities is to build very short stop spacing, as in Paris. Unfortunately, this imposes a sharp limit on train speed - and it's precisely the largest cities that have the most need for speed, since their suburbs usually stretch farther out of city center than those of smaller cities.

Metro construction is full of compromises. Cities that are building new systems, especially in the developed world, are likely to have so much sprawl, from decades of growing without a metro, that they need long stop spacing to serve the suburbs effectively. But they also are likely to have an organic central business district with many close-in dense neighborhoods, which would benefit from short stop spacing; they also have everywhere-to-everywhere commutes, as all modern cities do, which makes good interchanges between lines a must. Something has to give, and each city needs to figure out how, in its particular situation, to choose the optimal point in the speed-coverage tradeoff.

 
 
 
 

“One of the greatest opportunities facing our region”: Andy Burnham on making work better for older people

Andy Burnham (then health secretary) and Gordon Brown (then prime minister) meeting an older voter in 2010. Image: Getty.

In the Greater Manchester Strategy, published by the Combined Authority in October, we set out our vision for Greater Manchester, including our ambitions for employment.

It’s not simply about getting more people into work – though this is important, given that our employment rate across the region is still below the national average. It’s also about improving the quality of work; creating better jobs with opportunities for people to progress and develop. That’s why we’re working towards a Good Employer Charter to encourage businesses across the region to step up.

But if we want to make a real difference for the people of Greater Manchester, we need to focus on those who currently struggle most to find a job, including people with disabilities, people with fewer qualifications – and older people.

One in three people aged between 50 and 64 in the Greater Manchester area are out of work. Adding in older workers on low pay, nearly half (46.3 per cent) of 50-64 year olds in Greater Manchester are either out of work or in low paid, low quality jobs. This is a bad situation at any age – in your 50s, with fewer chances to get back into work and less time to make up the shortfall in income and savings, it’s terrible.

It’s also bad for the region. People out of work are more likely to have or develop health problems, and need more care and support from our public services. We are also missing out on the skills and experience of thousands of residents. If Greater Manchester’s employment rate for 50-64 year olds matched the UK average, there would be 19,000 more people in work – earning, spending and paying into the local economy. GVA in the region could grow by £800m pa if we achieved this. 

If it’s bad now, it’s only going to get worse unless we act. This is the fastest growing age group among working age people in Greater Manchester. And with the rise in State Pension Age, we are no longer talking about 50-64 year olds, but 50-65, 66 and eventually 67. There are more older workers, and we are working for longer. Many of us are now expecting to work into our 70s to be able to earn enough for our later lives.


As the State Pension age rises, older people without decent work must struggle for longer without an income before they can draw their pension. But if we approach this right, we can improve people’s lives and benefit our local economy at the same time. It makes financial and social sense.

Older people bring a wealth of knowledge and experience to the workplace, but we must make sure we provide a work environment that enables them to flourish. If we can help them get into good quality, suitable work, older people will be able to retain their financial independence and continue contributing to the region’s economy.

A report published earlier this week by the Centre for Ageing Better looks at exactly this issue. Part of our strategic partnership with the Centre for Ageing Better, the report is based on research conducted over six months with older residents in five communities with high levels of economic disadvantage across Greater Manchester.

In Brinnington, Stockport, the team met Adrian, in his late 50s. Adrian is a trained electrician, but since being made redundant ten years ago, has only managed to get a few short-term contracts. These short term, zero hours contracts, are “more trouble than they’re worth” and have left Adrian stressed and worse-off financially.

He has been sent on a large number of employment-related courses by JobCentre Plus, and has a CV with two pages listing training he has completed. However, these courses were of little interest to him and did not relate to his aim of finding stable work as an electrician. He told the team he only attended most of the courses so he “doesn’t get in trouble”.

Adrian recognises there are other types of work available, but much of it is warehouse based and as he is not in the best physical health he does not feel this work is suitable. He said he has “given up” on finding work – even though he still has 8 or 9 years to go until State Pension age.

Adrian’s story shows how badly the system is failing people like him – highly skilled, in a trade that’s in high demand, but being put through the motions of support in ways that make no sense for him.

A major finding of the report was the high number of people in this age group who had both caring responsibilities and their own health problems. With the need to manage their own health, and the high cost of paying for care, people found that they were not better off in low paid work. Several people shared stories of the complexity of coming off income support to take up temporary work and how this left them worse off financially – in some cases in severe debt.

The report concludes that changes are needed at every level to tackle chronic worklessness amongst this age group. This is not something that employment and skills services alone can fix, although Adrian’s story shows they can be much better at dealing with people as individuals, and this is something we want to do more on in Greater Manchester. But the health and benefits systems need to work in sync with employment support, and this is a national as well as a local issue.

Employers too need to do more to support older workers and prevent them from falling out of the labour market in the first place. This means more flexible working arrangements to accommodate common challenges such as health issues or caring responsibilities, and ensuring recruitment and other processes don’t discriminate against this age group.  

Greater Manchester has been at the forefront of devolution and has been using its powers to bring together health, skills and employment support to improve the lives of local people. The Working Well programme is a perfect example of this, providing integrated and personalised support to over 18,000 people, and delivering fantastic outcomes and value for money.

Such an approach could clearly be expanded even further to include the needs of older people. Ageing Better’s report shows that more can and needs to be done, and we will use their insights as we prepare our age-friendly strategy for Greater Manchester

We have to act now. In 20 years’ time, over a third of the population of Greater Manchester will be over 50. Making work better for all of us as we age is one of the greatest economic and social opportunities facing our city region.

Andy Burnham is the mayor of Greater Manchester.

For more about the work of Greater Manchester Combined Authority and its Ageing Hub, click here.