The early discussions on the justification for the Arc have focused on a rationale for a linear city since the initial National Infrastructure Commission report. The rationale, achieve urban agglomeration economies by merging labour markets. How linear transport connections road and rail. Although the expressway has fallen away we still have not yet got viable, zero carbon, model of urban form suitable for the Arc.
Those with long memories will remember the London-Stansted-Cambridge Corridor, now known as the Innovation Corridor. I remember naïve and never public consultants reports to Government quite literally proposing inking in several miles either side of the M42. I wrote an article in planning more than a decade ago criticising it. The Eddington Report into the East of England plan shared those criticisms. You can see it coming with the Arc. No wonder they don’t want an examination.
What is the problem? Linear cities don’t scale to the scale of development needed to meet the housing needs of the Arc. At this scale a linear city is the least efficient of all urban forms, hence it has limited capacity and will become, inevitably, car dominated and carbon spouting. Myself and many other have levelled similar criticisms about MBS’s plans for ‘The Line’ in NEOM Saudi, a scheme so bad that its management structure turns over every few weeks as it cant be justfied in economic or transport terms. Let me explain. I caution I will go on a bit as it is my specialist subject.
The early years of urbanism were based around compact concentric cities. The only exceptions were were local topography led to gridded urban forms becoming elongated (such as Berne) or development spread along a river Valley (such as Volgagrad, later Stalingrad, and Sarejevo) and many other river and coastal cities, especially in colonial areas.
This changed with the creation of rail and street cars. These allowed cities to expand beyond the walkable constraints of medieval walls. A key landmark was a proposal by Spanish engineer and philosopher Soria y Mata. Linear infrastructure would be developed along an optimal line from an existing city and the city would expand along that line.
This concept was adopted in Madrids Ciudad Lineal a 400m wide strip either side of a tramway.
Ernst May developed a linear city plan for Magnitogorsk as part of his contract for new Soviet Cities in the 1930s. Here a linear city made sense as there were topographic constraints in the River Ural Valley. His innovation was to make his Frankfurt Superblocks the building blocks. In the event little of the plan was built.
Nikolay Alexandrovich Milyutin outlined his concept of a linear city in in his 1930 book, Sotsgorod (Socialist City). The idea was to develop industrys along railway lines between raw materials and markets and to decentralise industry along them. Workers would live the opposite side of the railway line.
In 1969 the Italian Studio Superstudio developed
the Continuous Monument, a project dreamed up by Superstudio in 1969 – not as a proposal for a smart city, but as a critical warning against the relentless urbanisation of the planet. In a striking series of collages the designers depicted the vast blocky mass encircling the globe with an unstoppable belt of development, dwarfing the rocky outcrops of Utah’s Monument Valley, engulfing the Amalfi village of Positano and conquering Manhattan’s gridiron with its own inexorable grid.Rem Koolhaas, who encountered the photomontages of the Continuous Monument while he was a student at the Architectural Association in London. He was immediately enrapt. “I loved Superstudio because I took the work literally,” he explains, in an interview in the exhibition catalogue. “I thought some of it would be stunning if built.”
The Line, the super city proposed by MBS in KSA as part of the NEOM development is the latest and most dramatic exposition of the Linear city concept. An underground transport spine is supposed to link it all together. Th technology is not specified but it is assumed to be some form of hyperloop. This wouldn’t work as hyperloops are a-B technologies. You lose the pressure that powers the thing if you have an A-B-C-D etc. facility, let alone the very low capacities that hyperloops would have.
Linear Cities have great advantages in terms of infrastructure and phasing. The problem is its scalability. To be transit orientated you need stops every few hundred metres. The longer it is the more you have to stop. The more stops you have the less practical it is to have frequent fast through trains. If you run a railway solely on the principle of maximising fast train headway you have a system with no stops other than termini, a rail service serving no one in between. Also of course station headway causes delay. If you travel short distances in the centre of a linear city no problem, but the longer the line gets it becomes unreasonably lengthy. A good example of this is the many stations on the Marsden Vale line, such that it can take well over an hour o get from MK to Bedford. Indeed East West Rail is proposing fewer stations, with interleaved services, which would be better and could be nodes for high density development.
There are several means you can mitigate these problems. You can four track with through lines for fast services, you can have passing loops and interleaved services. These mitigate and don’t solve the scaling issue.
Compare with a radial city with total lines the same length as a linear city. Assume a number of stations and randomly chosen trip ends and origins. The radial city will perform better in term of travel time than the linear one. But this is not a real world model. In a small – medium scale town there will not be the demand or farebox to develop mass transit in all directions. In reality one linear corridor will be developed first, along the alignment that will generate most travel demand.
Consider also a scenario where there is a second mass transit line intersecting the first at a central high density node. This gives the opportunity to interchange at the most advantageous point and halves the travel time disadvantage for the same length of track compared to the same length of track in one linear city (with the adding time of waiting at the interchange). One could of course keep adding intersecting lines but henceforth you get diminishing returns. In many circumstances it is a grid of intersecting lines, with off grid trips done by conventional bus, that performs best. The grid city rather than the linear city.
Consider the Arc. We have that grid, the east-west rail connection, and the North-South Connections of the WCML, HS2, the East Coast Main Line and the West Anglia and Chiltern lines. So the critical points for sustainable urbanization then are where they interest. So how many are planned – one, yes just one, somewhere just South of St Neots. The extra capacity of the WCML wasted, no new links or nodes. The potential to link Bedford and Northampton on the former rail line wasted. Aylesbury a dead end. Calvert, nothing. The Arc will remain pass through country not connected country.
A zero carbon plan for the arc then but have a strategic zero carbon grid focused on the East West Rail AND new restored and optimised connections North South, maximising growth at the key connecting nodes. Otherwise relying only on East West Rail will only have the capacity for a small proportion of trips by non car modes, trips too long be attractive and forcing most growth onto the car.