The five technologies that changed the way we build cities

Without electricity, steel and lifts, there'd have been no Chrysler Building. Image: Getty.

Like most people who live in London, I spend an inordinate amount of time thinking about, or travelling on, public transport. And when walking around, I find myself constantly on the hunt for the shortest possible route from A and B. We city-dwellers tend to be a pretty impatient lot, and that can make us a bit blind to the details that surround us.

But I think it’s about time that we started to take notice of how the city works.

I’ve explored this very topic in my new book, Science and the City. It takes in cities on six continents, and looks at the technologies they’re using to change the urban landscape – as well as those developments from the lab that might utterly transform them in future.

Here is my own personal Top 5 – the five specific developments that, I believe, created the modern city.

1) Steel

Until the mid-1800s, large buildings were constructed from stone, brick and iron. All of these were strong but heavy, which limited how tall a structure could be before it began to collapse under its own weight.
To make taller buildings then, engineers needed a new material. So, they added small quantities (between 0.02 and 2 per cent) of carbon to iron, along with other impurities, to make an alloy. The steels produced were lightweight and easy to shape, while being hard and strong enough to form walls and foundations – perfect for use in tall buildings.

The alloys that were first developed in the early steel age gave birth to the railways, bridges, aircraft, cars, reinforced concrete, and, of course, the skyscrapers that now dominate our cities. For me, it's the king of urban materials.

2) Toilets

 

Ok, I’m cheating a bit here, because when I say toilets, I’m also referring to the sewers they empty into. Let’s start with this delightful thought. London’s sewers manage approximately 1.25bn kilograms of poo each year.
Before Joseph Bazalgette built his extensive sewer network, much of the city’s waste was discharged directly into the Thames. In Chicago, too, the uncontrolled mixing of water and waste led the city to take drastic action – they reversed the flow of their river, using a series of canals and locks.

It was the widespread adoption of plumbed toilets that first properly separated people from their waste, making the streets and waterways of the urban landscape considerably less smelly and more hygienic. It also kick-started the large-scale approach to water treatment that we all rely on today.

3) Electrification

A city’s electricity might be generated in any number of ways – from the burning of fossil fuels, through to wind energy from turbines. But electricity ultimately changed the world because it provided a way to rapidly and safely "pipe" energy to homes and businesses.

It was Thomas Edison who built the world’s first integrated power plant and grid system, and Nikola Tesla who figured out the best way to distribute the electricity it generated. Thanks to the resulting network, cities got electric streetlamps and escalators, trams, metros and trains, as well as homes full of labour-saving gadgets. Electricity also provided a way for city-dwellers to communicate over long distances – first, via the telegraph, later the radio, and now via cabled and wireless internet. Energy storage, however, remains a challenge facing every city.

4) Cars

While many of us try to avoid driving in the city, lots of the things we associate with urban life – traffic lights, road markings, signs and crossings – were all introduced to cities precisely because cars were on the road. 

The first motor vehicles had to be preceded by a person on foot, waving a red flag, but the invention of traffic lights changed all that. They also introduced structure to road networks, and gave pedestrians a place to cross. Road signage too is designed with a vehicle in mind: its retroreflective surface is designed specifically to be seen with headlights. 

If we get to a stage where the only cars on the road are driverless, our familiar street furniture could disappear entirely. Who needs a big shiny sign when a car could communicate with a sensor buried in the road?

5) Lifts

This one might seem a little controversial, but hear me out. Before the invention of the humble lift, living several storeys up was a pain. After them, tall buildings became practical, and top-floor apartments began to represent the ultimate in desirable city-living. 


In the centre of cities, where land has always been priced at a premium, going "up" rather than "out" became the norm, so skyscrapers started popping up everywhere. Lifts didn’t just change the way we did things – they built the city, and no-one could have predicted that outcome.

Lifts, and the skylines they created, may well have had a secondary impact too. A number of recent studies (such as this, or this) have suggested that densely-packed cities produce lower emissions, and are more energy-efficient, than those that have grown by low-rise sprawl.

The thing is, cities have never been as big, or as busy, as they are now. And while these five developments have given us a good foundation to work with, as our cities grow, we’ll need to find much better ways to power, clean, build, travel through and live in them. And for that, we’ll have to look to great science and clever engineering yet again.

What other technologies would you add to the list? Tweet me @laurie_winkless or using the hashtag #cityscience.

Laurie Winkless is a science writer based in London. Her book, Science and the City: The Mechanics behind the Metropolis will be published by Bloomsbury Sigma on 11 August.

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What does the Greater Manchester Spatial Plan mean for the region’s housing supply and green belt?

Manchester. Image: Getty.

We’re not even halfway through January and we’ve already seen one of the biggest urban stories of the year – the release of Greater Manchester’s new spatial plan for the city-region. The Greater Manchester Spatial Framework (GMSF) sets an ambitious target to build more than 200,000 homes over the next 18 years.

Despite previous statements indicating greenbelt development was off the table, the plan allows for some moderate easing of greenbelt, combined with denser city centre development. This is sensible, pragmatic and to be welcomed but a question remains: will it be enough to keep Manchester affordable over the long-term?

First, some history on Manchester’s housing strategy: This is not the first iteration of the controversial GMSF. The first draft was released by Greater Manchester’s council leaders back in October 2016 (before Andy Burnham was in post), and aimed to build 227,000 houses by 2037. Originally, it proposed releasing 8.2 per cent of the green belt to provide land for housing. Many campaigners opposed this, and the newly elected mayor, Andy Burnham, sent the plan back to the drawing board in 2017.

The latest draft published this week contains two important changes. First, it releases slightly less greenbelt land than the original plan, 4.1 per cent of the total, but more than Andy Burnham previously indicated he would. Second, while the latest document is still ambitious, it plans for 26,000 fewer homes over the same period than the original.

To build up or to build out?

In many cities, the housing supply challenge is often painted as a battle-ground between building high-density homes in the city centre or encroaching on the green belt. Greater Manchester is fortunate in that it lacks the density of cities such as London – suggesting less of a confrontation between people who what to build up and people who want to build out.

Prioritising building on Greater Manchester’s plentiful high-density city centre brownfield land first is right and will further incentivise investment in public transport to reduce the dependence of the city on cars. It makes the goal in the mayor’s new transport plan of 50 per cent of all journeys in Greater Manchester be made on foot, bikes or public transport by 2040 easier to realise.

However, unlike Greater London’s greenbelt which surrounds the capital, Greater Manchester’s green belt extends deep into the city-region, making development on large amounts of land between already urbanised parts of the city-region more difficult. This limits the options to build more housing in parts of Greater Manchester close to the city centre and transport nodes. The worry is that without medium-term reform to the shape of Manchester’s green belt, it may tighten housing supply in Manchester even more than the green belt already does in places such as London and York. In the future, when looking to undertake moderate development on greenbelt land, the mayor should look to develop in these areas of ‘interior greenbelt’ first.

Greater Manchester’s Green Belt and Local Authority Boundaries, 2019.

Despite the scale of its ambition, the GMSF cannot avoid the sheer size of the green belt forever: it covers 47 per cent of the total metropolitan area). In all likelihood, plans to reduce the size of the green belt by 2 per cent will need to be looked at again once the existing supply of brownfield land runs low – particularly if housing demand over the next 18 years is higher than the GMSF expects, which should be the case if the city region’s economy continues to grow.

An example of a successful political collaboration

The GMSF was a politically pragmatic compromise achieved through the cooperation of the metropolitan councils and the mayoral authority to boost the supply of homes. It happened because Greater Manchester’s mayor has an elected mandate to implement and integrate the GMSF and the new transport plan.

Other cities and the government should learn from this. The other metro mayors currently lacking spatial planning powers, in Tees Valley and the West Midlands, should be gifted Greater Manchester-style planning powers by the government so they too can plan and deliver the housing and transport their city-regions need.

Long-term housing strategies that are both sustainable and achievable need to build both up and out. In the short-term Greater Manchester has achieved this, but in the future, if its economic success is maintained, it will need to be bolder on the green belt than the proposals in the current plan. By 2037 Manchester will not face a trade-off between high-density flats in the city centre or green belt reform – it will need to do both.  If the city region is to avoid the housing problems that bedevil London and other successful cities, policy makers need to be ready for this.

Anthony Breach is an economic analyst at the Centre for Cities, on whose blog this post first appeared.