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.

 
 
 
 

To build its emerging “megaregions”, the USA should turn to trains

Under construction: high speed rail in California. Image: Getty.

An extract from “Designing the Megaregion: Meeting Urban Challenges at a New Scale”, out now from Island Press.

A regional transportation system does not become balanced until all its parts are operating effectively. Highways, arterial streets, and local streets are essential, and every megaregion has them, although there is often a big backlog of needed repairs, especially for bridges. Airports for long-distance travel are also recognized as essential, and there are major airports in all the evolving megaregions. Both highways and airports are overloaded at peak periods in the megaregions because of gaps in the rest of the transportation system. Predictions for 2040, when the megaregions will be far more developed than they are today, show that there will be much worse traffic congestion and more airport delays.

What is needed to create a better balance? Passenger rail service that is fast enough to be competitive with driving and with some short airplane trips, commuter rail to major employment centers to take some travelers off highways, and improved local transit systems, especially those that make use of exclusive transit rights-of-way, again to reduce the number of cars on highways and arterial roads. Bicycle paths, sidewalks, and pedestrian paths are also important for reducing car trips in neighborhoods and business centers.

Implementing “fast enough” passenger rail

Long-distance Amtrak trains and commuter rail on conventional, unelectrified tracks are powered by diesel locomotives that can attain a maximum permitted speed of 79 miles per hour, which works out to average operating speeds of 30 to 50 miles per hour. At these speeds, trains are not competitive with driving or even short airline flights.

Trains that can attain 110 miles per hour and can operate at average speeds of 70 miles per hour are fast enough to help balance transportation in megaregions. A trip that takes two to three hours by rail can be competitive with a one-hour flight because of the need to allow an hour and a half or more to get to the boarding area through security, plus the time needed to pick up checked baggage. A two-to-three-hour train trip can be competitive with driving when the distance between destinations is more than two hundred miles – particularly for business travelers who want to sit and work on the train. Of course, the trains also have to be frequent enough, and the traveler’s destination needs to be easily reachable from a train station.

An important factor in reaching higher railway speeds is the recent federal law requiring all trains to have a positive train control safety system, where automated devices manage train separation to avoid collisions, as well as to prevent excessive speeds and deal with track repairs and other temporary situations. What are called high-speed trains in the United States, averaging 70 miles per hour, need gate controls at grade crossings, upgraded tracks, and trains with tilt technology – as on the Acela trains – to permit faster speeds around curves. The Virgin Trains in Florida have diesel-electric locomotives with an electrical generator on board that drives the train but is powered by a diesel engine. 

The faster the train needs to operate, the larger, and heavier, these diesel-electric locomotives have to be, setting an effective speed limit on this technology. The faster speeds possible on the portion of Amtrak’s Acela service north of New Haven, Connecticut, came after the entire line was electrified, as engines that get their power from lines along the track can be smaller and much lighter, and thus go faster. Catenary or third-rail electric trains, like Amtrak’s Acela, can attain speeds of 150 miles per hour, but only a few portions of the tracks now permit this, and average operating speeds are much lower.

Possible alternatives to fast enough trains

True electric high-speed rail can attain maximum operating speeds of 150 to 220 miles per hour, with average operating speeds from 120 to 200 miles per hour. These trains need their own grade-separated track structure, which means new alignments, which are expensive to build. In some places the property-acquisition problem may make a new alignment impossible, unless tunnels are used. True high speeds may be attained by the proposed Texas Central train from Dallas to Houston, and on some portions of the California High-Speed Rail line, should it ever be completed. All of the California line is to be electrified, but some sections will be conventional tracks so that average operating speeds will be lower.


Maglev technology is sometimes mentioned as the ultimate solution to attaining high-speed rail travel. A maglev train travels just above a guideway using magnetic levitation and is propelled by electromagnetic energy. There is an operating maglev train connecting the center of Shanghai to its Pudong International Airport. It can reach a top speed of 267 miles per hour, although its average speed is much lower, as the distance is short and most of the trip is spent getting up to speed or decelerating. The Chinese government has not, so far, used this technology in any other application while building a national system of long-distance, high-speed electric trains. However, there has been a recent announcement of a proposed Chinese maglev train that can attain speeds of 375 miles per hour.

The Hyperloop is a proposed technology that would, in theory, permit passenger trains to travel through large tubes from which all air has been evacuated, and would be even faster than today’s highest-speed trains. Elon Musk has formed a company to develop this virtually frictionless mode of travel, which would have speeds to make it competitive with medium- and even long-distance airplane travel. However, the Hyperloop technology is not yet ready to be applied to real travel situations, and the infrastructure to support it, whether an elevated system or a tunnel, will have all the problems of building conventional high-speed rail on separate guideways, and will also be even more expensive, as a tube has to be constructed as well as the train.

Megaregions need fast enough trains now

Even if new technology someday creates long-distance passenger trains with travel times competitive with airplanes, passenger traffic will still benefit from upgrading rail service to fast-enough trains for many of the trips within a megaregion, now and in the future. States already have the responsibility of financing passenger trains in megaregion rail corridors. Section 209 of the federal Passenger Rail Investment and Improvement Act of 2008 requires states to pay 85 percent of operating costs for all Amtrak routes of less than 750 miles (the legislation exempts the Northeast Corridor) as well as capital maintenance costs of the Amtrak equipment they use, plus support costs for such programs as safety and marketing. 

California’s Caltrans and Capitol Corridor Joint Powers Authority, Connecticut, Indiana, Illinois, Maine’s Northern New England Passenger Rail Authority, Massachusetts, Michigan, Missouri, New York, North Carolina, Oklahoma, Oregon, Pennsylvania, Texas, Vermont, Virginia, Washington, and Wisconsin all have agreements with Amtrak to operate their state corridor services. Amtrak has agreements with the freight railroads that own the tracks, and by law, its operations have priority over freight trains.

At present it appears that upgrading these corridor services to fast-enough trains will also be primarily the responsibility of the states, although they may be able to receive federal grants and loans. The track improvements being financed by the State of Michigan are an example of the way a state can take control over rail service. These tracks will eventually be part of 110-mile-per-hour service between Chicago and Detroit, with commitments from not just Michigan but also Illinois and Indiana. Fast-enough service between Chicago and Detroit could become a major organizer in an evolving megaregion, with stops at key cities along the way, including Kalamazoo, Battle Creek, and Ann Arbor. 

Cooperation among states for faster train service requires formal agreements, in this case, the Midwest Interstate Passenger Rail Compact. The participants are Illinois, Indiana, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, and Wisconsin. There is also an advocacy organization to support the objectives of the compact, the Midwest Interstate Passenger Rail Commission.

States could, in future, reach operating agreements with a private company such as Virgin Trains USA, but the private company would have to negotiate its own agreement with the freight railroads, and also negotiate its own dispatching priorities. Virgin Trains says in its prospectus that it can finance track improvements itself. If the Virgin Trains service in Florida proves to be profitable, it could lead to other private investments in fast-enough trains.

Jonathan Barnett is an emeritus Professor of Practice in City and Regional Planning, and former director of the Urban Design Program, at the University of Pennsylvania. 

This is an extract from “Designing the Megaregion: Meeting Urban Challenges at a New Scale”, published now by Island Press. You can find out more here.