With the collapse of Londons Garden Bridge dream, the pitfalls of urban renewal programmes are more apparent than ever. So how do you emulate Manhattans High Line without sparking gentrification or becoming your metropoli into Disney World?

Every city craves a High Line. When Joshua David and Robert Hammond first dreamed of turning a long-disused elevated railway track overgrown with weeds into a linear park for Manhattan, they could scarcely have imagined the working day about 10 years and more than $180 m later when fellow urbanists in Miami, Seoul, Toronto, London and Sydney would strive to replicate their projects phenomenal success.

Part of the High Lines allure lies in its seeming impossibility, says Adam Ganser, vice president of planning and intend at Friends of the High Line. It was so unlikely that the proposed project would happen that I think it provides some optimism around similar crazy conceptions in other metropolis around the world. The reality that it attracts five million visitors per year and an estimated $980 m( 756 m) in tax revenue is also able to have something to do with it.

But as major cities fall over each other to accommodate the relics of their industrial past into engines of tourism and property booms, the chorus of detractors is developing. The charges against the mini-High Lines of the world are numerous: racial segregation, gentrification, expenditure, ugliness and outright idiocy. Londons Garden Bridge project has just collapsed amid widespread opponent from the very population it hoped to titillate. Even Hammond whose remorse included setting up the High Line Network, a bloc of decorators and planners meant to help other High Line-like adaptive reuse programmes avoid his mistakes acknowledges the problems. We were from the community. We wanted to do it for the neighbourhood, he said in a recent interview. Ultimately, we failed.

So, how do you do it right?

Sydneys
Sydneys version of the High Line, which offers a belief of Frank Gehrys famous Dr Chau Chak Wing Building. Photograph: Anna Kucera/ Destination NSW

Do: think of the locals first

While many people understand the High Line as the high watermark of urban issues Its perfect, pronounced the New Yorkers not easily pleased Peter Schjeldahl its critics accuse it of social failing. The High Line mob is overwhelmingly white, to a degree that is far out of line with the racial/ ethnic demographics of the borough and city, political scientist Alexander J Reichl reported in a paper last year. His observations that the level of racial homogeneity significantly outstrips that of other comparable parks, and that the lack of diversity cannot be explained by neighbourhood composition produced him to the conclusion that the High Line is fail as a democratic public space.

Among its unintended negative consequences is gentrification of many kinds, from some of the most expensive residential real estate, to the disappearance of taxi garages and gas stations, to the displacement of art galleries that stimulated Chelsea appealing in the first place, says architecture critic Alexandra Lange. The condos along the High Line are disproportionately pricier than their neighbours, with Bjarke Ingels and Zaha Hadid among the architects who have cashed in.

Worse, is the lack of appeal of the High Line for long-time community residents a destination park without being a neighbourhood amenity, says Lange. In the New York Times, writer Jeremiah Moss has deplored it as a tourist-clogged catwalk and merely another chapter in the histories of New York Citys transformation into Disney World.

Dont: merely do it anywhere

The High Lines mistakes are artfully multiplied and layered, says urbanist James Howard Kunstler. For instance, the assumption that New York City doesnt require railroad tracks anymore. Or the idea that buildings dont have to relate to the street-and-block grid. Instead of repairing the discontinuities of recent decades we just celebrate them and make them worse.

But a good part of the High Lines success, in the opinion of architecture prof Witold Rybczynski, is due to its architectural fixed, which, like the 12 th arrondissement, is mobbed with interesting old and new houses. Other than New York, very few American metropolis can offer the same combination of history and density.

In other terms, there is a danger that what works in a specific place might fail in other less interesting landscapes. Done wrong, High Lines could become the latest in a long list of urban issues failures, such as downtown shopping mall, underground passageways, skyways and monorails.

Sydneys unloved monorail, which opened in 1988 merely to close only 15 year later, inspired one architecture firm to propose converting it into a garden path called wait for it the High Lane. The programme never got enough traction to stop the monorails demolition, but in 2015 the city got its own elevated linear park anyway: the Goods Line. Its a much closer imitation of the High Line, built upon disused industrial railway way and outfitted with greenery, wifi, performance spaces and even an outdoor gym.

The architectural texture of Sydney, a city developed mostly in the postwar car-centric age, cant compete with that of New York and Paris or even that of Melbourne, where a historic railway bridge comes up every so often as a candidate for High-Lineification. But the Goods Line at least offers a striking view of Frank Gehrys characteristically unconventional Dr Chau Chak Wing Building at the University of Technology Sydney. Its a decent start.

Dont: construct it from scratch

Seattle hired High Line landscape architect James Corner to design a 26 -block promenade, linear but not elevated, that would replace an unsightly road, which was to be relocated underground. But the project came face to face with Kate Martin, another decorator who was intent on saving a section of the condemned road for converted into an unusually high High Line.

After unsuccessful school board and mayoral campaigns, Martin attained the Park My Viaduct project her political mound on which to die. Even after her seismic engineer ruled out the possibility of retrofitting the existing freeway, she proposed rebuilding some of it after the demolition. The programme won merely 19% in a local referendum , not least because Corner himself described Park My Viaduct as a dumb notion. The High Line doesnt stand out alone, apart from the city, he said.

Until lately, London seemed as though its own High Line would take the form of a park spanning the Thames. The Garden Bridge was originally envisioned in 1998 by Absolutely Fantastic actor Joanna Lumley as a tribute to Princess Diana. It was different from the New York High Line, in that it would have to be built from scratch. But as expenditures passed 200 m with the city likely to be liable for ongoing maintenance and Londoners grew displeased with the proposals to limit public gatherings on the bridge, mayor Sadiq Khan withdraw fiscal guaranties, effectively killing it.

Joanna
Joanna Lumley in 2015 at the site of the proposed Garden Bridge across the river Thames. Photo: Philip Toscano/ PA

Do: crowdfund for extra legitimacy

As Khan taketh away, so he giveth: the Camden Highline aims, like its inspiration in New York, to make a park out of an existing qualify way in this case a 2,800 ft stretching between Camden Town and Kings Cross, originally part of the North London Railway, which discontinued procedures in 1922.

[ Its] a great example of a local community taking an idea and garnering supporting in order to make it a reality, says Khan, referring to the fact that the Camden Highline raised the first phase of its budget, 63,976, on the crowdfunding platform Spacehive.( The mayor himself pitched in 2,500.) Spacehive previously crowdfunded feasibility assessments for a potential Peckham Coal Line, an elevated urban park in southern London made from old coal sidings.

Dont: belief crowdfunding is enough, however

This kind of Kickstarter urbanism, nonetheless innovative, has its limitations. You wouldnt Kickstart a replacement bus line for Brooklyn, but you might Kickstart an app to tell you when the bus on another, less convenient line might come, Lange has argued.

Take the Lowline, an abandoned trolley terminal in New York that was billed as the worlds first underground park. The crowdfunding campaign developed considerable attention but in reality the park was a wildly overambitious proposition, with the funding merely able to cover a test run of the skylights that would filter daylight underground.

Garden
The High Line that could have been … Londons failed Garden Bridge. Photograph: Thomas-Heatherwick designs

Do: design it well

Lange likewise criticises the Lowlines vision of a high-tech eco-tainment traversed with a multi-purpose community centre, assuring something undeniably dystopian about the idea that a neighbourhood starved for open space might find its solution in a passageway. Indeed, the High Line has been substantially created public expectations for design.

Chicagos Bloomingdale Trail, another railway-turned-park that acts as the backbone of a larger network called the 606( taken away from the citys zip codes ), opened in 2015 to a collective shrug from a city that boasts such famously well-executed public spaces as Millennium Park. The fact that the 606 is an elevated trail on an abandoned rail line makes an virtually inevitable comparison to New Yorks High Line, wrote urbanist Aaron Renn. The 606 is not even remotely another High Line.

He argued that it doesnt have any citywide significance, either for local residents or for tourists. Its a neighbourhood-serving railing road that is elevated above the streets with some nicer features like illuminating that you dont read often but its affected with a utilitarian awkwardness owing to its low budget ($ 95 m merely over half the cost of the High Line) and the various requirements of the regulatory bodies involved.

Do: look in unexpected places

Torontos Bentway, slated to open at the end of this year, is one of the most powerful pretenders to the High Line throne. In Torontos case, private philanthropists applied urban consultants to magistrate what Toronto actually needed in the way of parks and where. The undervalued ground they identified lies beneath the regrettable Gardiner Expressway, a mid-century road that cuts off the citys waterfront.

The Bentways continuous, road-shaded route will have 55 outdoor rooms demarcated by the Gardiners concrete support structures( or bents ), variously appropriate for gardens, art shows, playgrounds, farmers marketplaces, performance spaces, and much else besides ideally upending the longstanding North American perception of the ground under roads as being useless, unclean or outright dangerous.

Similarly, Miamis Underline aims to make a 10 -mile linear park, urban trail and canvas for art out of the land beneath its railway system elevated trail, currently used for either parking or nothing at all.

Seouls
Seouls Skygarden a successful version of Londons Garden Bridge? Photograph: Ossip van Duivenbode

Do: be patient, young Jedi

In search of a High Line of its own, Seoul picked a freeway overpass that had become unsuitable for vehicles. Rather than tear it down, the city reinforced it and, with a designing by Dutch landscape architect Winy Maas, turned it into an artfully lighted elevated park lined with flowers and attractions, connected immediately to the towers around it, and open 24 hours a day. What differentiates Seoullo 7017, as Rowan Moore wrote for Guardian Cities on its opening in May, is the ambition to grow out of the character and be necessary for contemporary Seoul, and as such it promises to be among the more convincing of all the many High Line wannabes in the world.

While it still retains a little bit of the stark, concrete appear of midcentury Seoul, the parks designers are urging the public to give its organic features a chance to emerge as have those of the Cheonggyecheon, the celebrated downtown river that replaced another 1970 s road flyover in 2005.

Its a fair point: these projects are about deep-rooted change, a shift in priorities from pure economic capacity to aesthetics, convenience and public amenity. Stimulating sure that potential is leveraged to benefit the existing communities that live near these projects, and benefit the park as well, will be key to their long-term success, says Ganser.

And as glorious a view as they can provide, Lange advises their inventors not keep forgetting about the foreground. Belief about the park in the framework of the city and the neighborhood, of different age groups and use groups. Dont allow it to drive away the person or persons it is unable to most benefit. Each opportunity is a chance to attain the idea of an infrastructure park more complete which goes down lane deeper than design.

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