Here’s how developing world cities can plan for the next half century of rapid urban growth

Can Tho, Vietnam, 2017. Image: Getty.

 Cities continue to grow at a rapid rate. Within the 100 Resilient Cities Network, more than half of the cities in Latin America, Asia, the Middle East, and Africa are seeing their population expand by 2 per cent or more annually – the benchmark of rapid urban growth.

A metropolis like Lagos, Nigeria demonstrates how drastic this can be: increasing from 7.1m to 9.8m residents between 2000 and 2015, its population is expected to more than triple to 34m by 2050.

To begin to understand what this means for urban resilience, 100RC has collaborated with New York University’s Marron Institute to develop urban growth projections for 20of our most rapidly expanding cities located in the Global South.

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A growing population may increase density in central areas, but it also has the effect of dramatically expanding a city’s physical boundaries. Population density in cities is, on average, declining by 2 per cent per year, and almost every city globally is experiencing significant spatial expansion as a result – including some that have no population growth, and even a few that are losing population.

Nairobi, Kenya, for example, is forecast to increase its total area 5.3-fold by 2050; in that same time frame, the twenty cities in this study will on average increase their total area 3.7-fold.

As these cities continue growing outward, a significant amount of work must be undertaken to not only provide for projected expansion but also to guide its development. Almost all of the infrastructure that will have to accommodate this growth has yet to be built, presenting a significant opportunity to plan for expansion in an efficient and equitable manner that contributes to the city’s overall resilience.


To be truly impactful, a city Resilience Strategy must not only consider existing urban areas but also account for projected urban growth and use it as an opportunity to accelerate resilience-building. Failure to plan and organise the expansion areas of cities is the root cause of a number of serious resilience challenges: housing affordability, traffic congestion, poor access to labour markets and public space, natural hazard risk to communities, loss of natural environment and ecosystems, and lack of basic services such as water, sanitation, and electricity. 

It also costs more. The expense of bringing critical infrastructure into existing communities is 3 to 9 times higher than the cost of installing the basic trunk infrastructure in planned communities, incrementally, in advance of development.

Satellite imagery at three discrete points in time (1990, 2000, and 2014) has been used to assess the quantity and quality of the urban growth in this period and to support the development of urban growth projections through 2050. Here we present a handful of key indicators that the Marron Institute uses to characterise the quality of urban growth, each of which has particular implications for urban resilience: average city block size, street width, proximity of residential areas to arterial roads, and percentage of open space available for residents.

Quantifying urban expansion

As cities grow, they must also contend with administrative and geographic boundaries. Once an urban centre expands beyond a single jurisdiction, the resulting regional fragmentation adds extra complexity to city governance and must be factored into planning processes.

This challenge is currently being confronted by several metropolitan areas within the 100RC Network. For example, the UK city of Manchester and its surrounding boroughs came together in 2010 as the Greater Manchester Combined Authority, thereby giving more planning autonomy to the metropolitan region, rather than each council independently planning for a system that affects the metropolitan area as a whole.

While most of Byblos’ urban region falls within its municipal boundary, Buenos Aires’s urban region mostly falls outside of city jurisdiction.

Da Nang, Vietnam, has the highest urban growth rate within the 100RC network; the metro area expanded by 5.6 per cent annually between 2000 and 2014.

Most of its recent growth extended well beyond the city’s administrative boundaries and into adjoining areas. This poses challenges for integrated spatial planning and may call for more active regional planning to compensate for the resulting fragmentation, as described above.

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The shape of a city as it grows also has implications for urban resilience planning. The image above demonstrates that, over the years, Can Tho has elongated and become less dense. This has significant impacts on transportation within the urbanised area, where the average commuting time to the city centre becomes higher than in more circular cities and where greater difficulties arise in managing an extended system. Already existing environmental challenges caused by pollution are additionally exacerbated, meaning that urban form holds a direct impact on a city’s chronic stresses.

Streets and walkability

Multimodal streets are a unique characteristic of urban areas. Four-way intersections in particular improve accessibility not only for drivers, but also for pedestrians and cyclists. They minimise trip distance for greater walkability and cycling as well as increase route options, which in turn can decrease congestion and vehicular traffic.

A lower share of four-way intersections reduces the route choice within a given area, increasing the changes of congestion and impeding walkability. Edited for clarity, these satellite images demonstrate that Santa Fe, Argentina has a higher percentage of these intersections (46 per cent) than does Byblos, Lebanon (6 per cent).

The average size of a city block also affects how accessible a neighbourhood is. Residential blocks that measure more than 4 to 5 hectares begin to impede walkability, by increasing the distance between points.

In Cali, Colombia, for example, the city’s older area is easier to navigate on foot than its newly-developed districts. A city’s level of walkability is important for promoting public health objectives, cohesive and engaged communities, and a number of other urban resilience benefits.

Average city block size in Can Tho, Vietnam far exceeds that of Cali, Colombia, implying that the latter’s neighbourhoods are more accessible to pedestrians.

Arterial roads

When planned effectively, arterial roads support urban resilience by linking residents to jobs, providing vulnerable and underserved communities access to basic services like water and power, and allowing for generally greater mobility around a city. Arterial roads carry public transportation and trunk infrastructure such as water supply, power and telecommunications and, as a public good, must be planned and implemented through government action. They are far more cost-effective and efficient to provide if created in anticipation of settlement, before development occurs in that area.

Ideally, every resident would live within walking distance of a road that can efficiently carry public transportation – even if that system is not yet in place. For this reason, the Marron Institute has studied the proximity of built-up areas to arterial roads as a key metric in the quality of urban expansion; it has additionally developed the Making Room methodology of planning a grid of arterial roads in areas of projected urban expansion and working with local government to secure rights of way to these corridors in advance of development.

Addis Ababa exhibits a shortage of wide arterial roads in the area developed between 1986 and 2017. Prior to 1986, the city exceeded global and regional norms, but it is now statistically similar to those values, and the share of land with access to this type of road has declined by 26 percentage points.

Projections

Based on overall global trends, the cities in the study are expected to continue their outward expansion, declining in urban density at an annual rate of 1-2 per cent, while increasing their land consumption in some cases up to 7-fold by 2050.

The graphic below organizes the participating cities by their expected population growth rates, and shows their projected growth in area over the next 35 years. In that timeframe, Can Tho, the fastest-growing city from 2000-10, is expected to experience population growth of 114 per cent and add as much as 26,000ha to its territory, representing a 5-fold increase in total area. Medellin, on the other hand, is on a path toward a 40 per cent increase in population and add as much as 43,600ha, or a 1.6-fold increase in total area.

Click to expand. Cities are organised from left to right, top to bottom, by their expected percent increase in total area by 2050, given a 2 per cent decline in population density.

Next steps

The 20 cities in the NYU study are currently working to incorporate these findings into their Resilience Strategy development and implementation. We hope the findings will influence existing project development and lead to new initiatives focused on planning in advance for urban growth in a way that supports the broader resilience of cities.

Rebecca Laberenne is associate director, innovation in the built environment, City Solutions at 100 Resilient Cities. Patrick Lamson-Hall is research scholar at NYU Stern Urbanization Project.

This article previously appeared on the 100 Resilient Cities blog.

 
 
 
 

How can cities become more bike friendly? The Netherlands offers useful lessons

(Aurore Belot/AFP via Getty Images)

It might seem like cycling is in the DNA of the Netherlands, a country where even the prime minister takes his bicycle to work. But the Dutch haven’t always lived as one with their bikes. In the Amsterdam of the early 1970s, cars were considered the wave of the future. They can be seen filling up squares and streets in historical photographs, and killed an average of over two Amsterdammers per week, including many children.

It is nothing more than an “accident of history” that the Netherlands embraced cycling, says Marco te Brömmelstoet, the director of the Urban Cycling Institute in Amsterdam and a man better known as the city’s cycling professor. Today’s bike rider’s paradise was created after parents and activists took to the streets to protest “child murder” by car. A Saudi oil embargo, rising gas prices, concerns about pollution and anger about the destruction of entire neighbourhoods to build motorways did the rest. 


Amsterdam, 1958. Not a cyclist's paradise. (Keystone/Getty Images)

What’s important about this history is that it can be replicated in other cities, too. Of course, the Netherlands has certain advantages – it’s flat as a pancake, for example. But in the eyes of traffic reformers, the rise of e-bikes (and even cargo bikes) means there’s no excuse for prioritising cars everywhere. 

So how can cities, flat or not, follow Amsterdam’s path to creating places where cycling is a pleasant, safe and common way to get around? The Dutch have some tips. 

Separate bikes from car traffic

Any city could start painting dedicated bike lanes on the streets. But in the Netherlands, those white marks indicating space for cyclists are considered just a minor first step. 

“A line on the road is not enough. Motorists will ignore it,” says Frans Jan van Rossem, a civil servant specialising in cycling policy in Utrecht. If other cities want their residents to choose bikes instead of cars when dodging pandemic-era public transport, protecting them from fast-moving car traffic must be the priority, Van Rossem says. 

The Dutch research institute CROW developed a widely praised design manual for bicycle infrastructure, full of tips for creating these protected lanes: A row of vertical white posts or a curb can serve as a physical separator, for example. Still, cyclists tend to feel safest in a "solitary" path, separated from the road by grass, trees, or an elevated concrete island. 

“The main bottleneck, the main reason why people don’t cycle, is that they don’t feel safe,” Van Rossem notes. “To start, construct separate paths.”

Turn those bike paths into a network

Many cities may have some bike lanes on some streets, but leave cyclists to roll the dice everywhere else. Will conditions still be safe when they turn left or right? Often they have to continue their way without any protected facilities for cyclists. 

“In many cases, cities take fast action, without thinking it through very well,” says Lucas Harms. He leads the Dutch Cycling Embassy, a partnership between the Dutch government and several companies, which promotes Dutch bike knowhow globally. “Don’t build small pieces of bike lane from nothing to nowhere. Think about a network of cycling infrastructure.” 

Utrecht aims to have cyclists within 200 to 300 metres of a connected path anywhere in the city, Van Rossem says. Avoid constructing those paths in sketchy industrial areas, he warns. “A connection through an unattractive area may be fast, but won’t be used a lot.”

Embrace the ‘fietsstraat’, a street where bikes come first


On some streets, drivers have to give up their privileges. (Rick Nederstigt/AFP via Getty Images)

A peculiar Dutch invention called "fietsstraat" (cycling street) holds strong potential for the rest of the world, Kevin Krizek says. He’s a transportation professor from Colorado who spent three years at Radboud University in Nijmegen. 

On cycling streets, cars are “guests”, restricted by a speed limit of 30 kilometres per hour. Drivers are not allowed to pass, so cyclists comfortably dominate the road. In the Netherlands the fietsstraat is usually paved with red asphalt, to resemble a bike path and notify drivers of their secondary status. But creating a cycling street can be easy. “All you need to do is put signs at intersections,” Krizek says. The effect is revolutionary in his view. Drivers have to give up their privileges, and cyclists can take the lead. 

Some Dutch traffic experts worry the cycling street won’t work if a city doesn’t also have a robust cycling culture. In the Netherlands, drivers are aware of the perils of urban cycling because they too use bicycles. Moreover, Dutch cities use sophisticated “circulation plans” to direct cars away from city centres and residential areas, onto a few main routes. 

Without “calming” traffic this way, the cycling street could be a step too far, Harms says. “In a city like New York, where all roads are equally accessible and full, it’s better to separate bicycles and cars,” he says.

Redesign intersections for cyclists' safety

If cyclists have to cross intersections “at the mercy of the Gods”, you’re not there yet, says Harms. When he travels abroad, he often finds clumsily designed crossings. As soon as cars turn, cyclists may fear for their lives. 

Harms recommends placing physical barriers between cars and bikes in places where they must cross. The Dutch build elevated islands to direct traffic into separate sections. The golden rule: cars wait behind bicycles. That way, drivers can see cyclists clearly at all times. Barriers also force Dutch cyclists to turn left in the safest way possible. They cross the street first and wait for their turn again before making their way left.

“You can create that with simple temporary measures,” Harms says. Planters work fine, for example. “They must be forgiving, though. When someone makes a mistake, you don’t want them to get seriously injured by a flower box’s sharp edge.”

Professor Krizek points out how the Dutch integrated cycling routes into roundabouts. Some are small; some are big and glorious, like the Hovenring between Eindhoven and Veldhoven, where cyclists take a futuristic-looking roundabout lifted above the highway. Most of those traffic circles move high volumes of cars and cyclists through intersections efficiently and safely. For a simpler solution, the Dutch manual suggests guiding cyclists to quieter streets – crossing a block up or down may be safer. “Nobody knows how to do intersections better than the Dutch,” says Krizek. 

Ban cars, or at least discourage them


A man rides down from a three-level bicycle parking garage near Amsterdam's main train station. (Timothy Clary/AFP via Getty Images)

The quickest, most affordable way to make a city more bikeable is to ban cars, says Ria Hilhorst, cycling policy advisor for the City of Amsterdam. It will make streets remarkably safe – and will most likely enrage a significant amount of people. 

Amsterdam doesn’t outlaw cars, but it does deliberately make their owners feel unwelcome in the historic city’s cramped streets. Paid parking is hugely effective, for example. Many car owners decide to avoid paying and use bicycles or public transportation for trips into the city. Utrecht, meanwhile, boasts the world’s largest bicycle parking garage, which provides a dizzying 12,500 parking spots.

To further discourage drivers from entering the city’s heart, Amsterdam will soon remove more than 10,000 car-parking spaces. Strategically placed barriers already make it impossible to cross Amsterdam efficiently by car. “In Amsterdam, it is faster to cross the city on a bike than by car,” Harms says. “That is the result of very conscious policy decisions.”

Communicate the benefits clearly

Shopkeepers always fear they will lose clients when their businesses won’t be directly accessible by car, but that’s a myth, says Harms. “A lot of research concludes that better access for pedestrians and cyclists, making a street more attractive, is an economic boost.”

Try replacing one parking space with a small park, he recommends, and residents will see how it improves their community. Home values will eventually rise in calmer, bike-friendlier neighbourhoods without through traffic, Van Rossem says. Fewer cars mean more room for green spaces, for example.

“I often miss the notion that cycling and walking can contribute a lot to the city. One of the greatest threats to public health is lack of exercise. A more walkable and bikeable city can be part of the solution,” says Ria Hilhorst. “But in many countries, cycling is seen as something for losers. I made it, so I have a car and I’m going to use it, is the idea. 

“Changing this requires political courage. Keep your back straight, and present a vision. What do you gain? Tranquility, fewer emissions, health benefits, traffic safety, less space occupied by vehicles.” 

Again, she points to Amsterdam’s history. “It is possible; we were a car city too.”

Karlijn van Houwelingen is a journalist based in New York City.