Skyways: a strategy to humanize the mobility of the vertical cities

Adrián Martínez-Muñoz, Int. J. Transp. Dev. Integr., Vol. 5, No. 4 (2021), 393–404 © 2021 WIT Press, www.witpress.com ISSN: 2058-8305 (paper format), ISSN: 2058-8313 (online), http://www.witpress.com/journals DOI: 10.2495/TDI-V5-N4-393-404 SKYWAYS: A STRATEGY TO HUMANIZE THE MOBILITY OF THE VERTICAL CITIES ADRIÁN MARTÍNEZ-MUÑOZ Department of History, Theory and Architectural Composition, University of Seville, Spain ABSTRACT The lack of contemporary theoretical support for the construction of the vertical city leads to the application of an inherited model, conceived almost a century ago. Therefore, the urban space suffers a strong dehumanization, disconnecting the inhabitants from the urban context. In the search for strategies to make the high-rise city of the coming decades more humane, it is worth proposing the hypothesis of a hyperconnected, three-dimensional and multilayered vertical city: a mesh of pedestrian skyways between skyscrapers that reproduce streets and urban squares where citizens can socialize. This paper proposes a rereading of those experiences and projects that, from the beginning of the 20th century to the present, built or unrealized, contributed to elaborating a new ideology about elevated pedestrian mobility. These ideas elevated the social and the relational, away from ground level through skyways to find growth strategies at the human scale, and so declaring the age of the multilevel city. Keywords: pedestrian mobility, human scale, multilevel city, skybridges, skyways, vertical city 1 INTRODUCTION Hundreds of vertical developments, with the residential tower typology as the cornerstone, spread throughout the main megalopolitan concentrations, especially in the Asia-Pacific region. The rapid urbanization of cities prevents a deep reflection on the appropriate model to follow. Planners, overtaken by a rising real estate market and political pressure, continue with the modern idea of converting quantity – overpopulation – into quality through abstraction and repetition: residential mega blocks distributed and repeated relentlessly over the territory. At this massive scale, the hypothesis of a hyperconnected, three-dimensional and multilayered city could be offered as a way to rethink the vertical city, with the goal of humanizing the urban model. This hypothesis is also a reflection on mobility where the concept of walkability is re-evaluated regardless of verticality and seen as a powerful tool to create a more livable and sustainable city. Skyways, as bridges between skyscrapers dedicated to pedestrians, can play a fundamental role in the quality of the urban environment. This paper studies the urban phenomenon of skyways in three steps. Firstly, the text succinctly examines the history of the multilevel city with the focus on elevated pedestrian systems. Secondly, a group of skyways, which are situated in real contexts, will be analysed. Finally, one experience and three projects from the architectural discipline will be reviewed to discover some strategies about mobility close to the clouds. The Journal of Transport Development and Integration has been selected because it involves the field of research closest to our subject of investigation. Although the concepts of sustainability, city planning and human comfort are closely related to the subject of this paper, it is within the field that deals with the integration of the different forms of mobility and their harmonization in the city, where the debate could find a better audience. 394 Adrián Martínez-Muñoz, Int. J. Transp. Dev. Integr., Vol. 5, No. 4 (2021) 2 METHODOLOGY In order to provide a new strategy to challenge the vertical city based on modern principles and achieve models which could generate a more humane city from the mobility perspective, this paper establishes a methodology based on some conceptual developments and projects. These projects, primarily from the twentieth century, were based on a mesh of skyways and proposed to elevate pedestrian mobility as a duplication of the ground level. Firstly, a survey of the history of architecture was done, particularly in search of projects and case studies produced by other architects who worked with the idea of radically introducing a fragment of urban space at a certain height: skyways, skywalks, pedways and footbridges. Also, an initial study of existing peer-reviewed journal papers, historical archives, news articles, existing performance data on vertical transportation, etc., was carried out. Secondly, after the initial selection, fundamentally from the 20th century to the present, these projects and examples were ordered and categorized. In addition, the author has participated in international workshops and seminars on the subject. Interviews and feedback from these encounters have been incorporated into the overall research. Thirdly, a critical analysis and comparison using a systematic set of principles and criteria between the projects of the same ‘category’ was done, with the target of defining a new way to rethink the vertical city. 3 A BRIEF HISTORY OF THE MULTILEVEL CITY The publisher Moses King, driven by the ambition to predict the city to come and the hectic pace of the laissez-faire building of New York, published in 1896 the first edition of his King’s Views of New York guide series. In this and subsequent editions, King recorded through photographs and drawings the rapid change that the island of Manhattan was undergoing. The covers that illustrated the 1908 King’s Dream of New York and the 1911 King’s Views of New York editions, which were commissioned from two architects, Harry M. Pettit and Richard Rummell respectively, deserve special attention. Both frontispieces were inspired by problems that were beginning to condition Manhattan at the beginning of the century, such as the impact that skyscrapers and increased vehicular Figure 1: Tianjin, China (picture by the author). Adrián Martínez-Muñoz, Int. J. Transp. Dev. Integr., Vol. 5, No. 4 (2021) 395 traffic had on the ground, and therefore, on pedestrians. The cover drawn by Pettit, titledThe Cosmopolis of the Future (Fig. 2), answered the commission with a futuristic vision of tiered skyscrapers plus a multilevel circulation system. On the one hand, the terraced skyscraper was drawn as a way to bring light and air to the lower levels of the congested streets of New York, and on the other hand, a multilevel mobility network was imagined as an efficient tool to organize a large number of vehicles and people that flooded the city every day. Although separated by only three years, the worlds portrayed in both illustrations showed certain differences. In 1908 Pettit, despite a sky overcrowded by huge aeroplanes, revealed an urban world dominated by pedestrians crowding skyways and elevated bridges. The 1911 cover titledThe Future of New York is Pre-eminently the City of Skyscrapers (Fig. 2), drawn by Rummell, portrayed a city dominated by machines: extensive rail networks on bridges instead of pedestrians, streetcars, and automobiles on the ground floors. Even the setbacks (terraces and balconies) were emptied of inhabitants to give all the prominence to the mechanization of the urban space that so excited thinkers at the beginning of the century. The illustrators who accompanied Moses King were not the only ones who envisioned a future city spread out in space. In the same year as the Harry M. Pettit image, another artist composed the cover that opened Man’s Machine-Made Millennium (Fig. 2), published by chemist and inventor Hudson Maxim in Cosmopolitan magazine in its November 1908 issue. The visionary illustration, carried out by the successful American artist William Robinson Leigh, showed a great city as a huge building. A kind of spatial framework, massive at times, with infinite bridges that jumped in all directions over the deep avenues: some loaded with pedestrians, others like traffic routes that pierced the built mass of the enormous buildings. The now-defunct New York Tribune newspaper, in its print run on Sunday, January 16, 1910, published a full-page drawing that returned to the three-dimensional city in several layers and levels. Inside the newspaper, a column titled Sees future New York: Sidewalks in layers and other wonders in Mr. Suplee’s Ken (Fig. 3) could be read. Strangely, three years later, the same lightly tweaked drawing appeared in the weekly Scientific American in late July, illustrating The Elevated Sidewalk: How it will solve City Transportation Problems (Fig. 3) Figure 2: (A) ‘King’s Dream of New York’ by H. M. Pettit in 1908 [1]; (B) ‘King’s Views of New York’ by R. Rummell in 1911 [2]; (C) Drawing by W. R. Leigh, 1908 [3]. 396 Adrián Martínez-Muñoz, Int. J. Transp. Dev. Integr., Vol. 5, No. 4 (2021) by engineer Henry Harrison Suplee, apparently the same author from the New York Tribune article. The main difference between these almost twin images was centred on the accumulation of traffic on the ground floor. Once the city had been organized on different levels, with pedestrians roaming freely on the upper sidewalks, the biggest advance focused on transportation. While the 1910 cover showed cars winding freely, the 1913 cover presented a tram in the centre that separated the large avenue in two. In 1929, the New York Regional Plan asked various experts for proposals to solve the congestion which was blocking Manhattan. Harvey Wiley Corbett, a prominent architect and professor at Columbia University, presented an ambitious plan for the separation of vehicular and pedestrian traffic, largely based on reformulations of his earlier studies from 1923 of the city at various levels. The proposal, developed with the perspectivist Hugh Ferriss (Fig. 4), was conceived as a multilevel city with several infrastructures for traffic and pedestrian in all directions. Skyscrapers of this imagined city were connected in a continuous skyway. The proposal was a kind of highly modernized Venice in which the canals were flooded by vehicles instead of water, solving congenital congestion through shock therapy: multiplying traffic. At other side of the Atlantic, even though Italian futurists and Russian constructivists produced a certain machinist iconography concerning buildings and cities connected at certain heights, the chronicle of the European reaction to the typology born overseas pointed to Le Corbusier’s urban approaches. HisContemporary City for Three Million Inhabitantsexhibited at the Salon d´Automne in 1922, planted the seed of the principles that defined the Corbusian ideals against the problems of the nineteenth-century city: an urban architecture of ‘air, vegetation, sun and the car’. A Cartesian city composed of cruciform skyscrapers that, devoid of any singularity, became the isotropic and mechanical element that infinitely dotted the territory. The City Towers(1922), by August Perret, was a model that Le Corbusier surely had in mind while he projected his idea of the city. However, he eliminated from Perret’s project the element that most interests this paper: the skybridges that linked the towers. He did so because he considered them dangerous. Figure 3: (A) Newspaper New York Tribune 16th January 1910 [4]; (B) Scientific American magazine 26th July 1913 [5]. Adrián Martínez-Muñoz, Int. J. Transp. Dev. Integr., Vol. 5, No. 4 (2021) 397 Hilberseimer projected his model of the city in parallel to Le Corbusier, surely more in tune with what was taking place on the other side of the ocean. In 1924 he presented a city approach based on the section, on the stacking of uses, instead of the Corbusian horizontal zoning. The project, known as Vertical City or Hochhausstadt (Fig. 5), proposed a dense and three-dimensional city, both in terms of uses and mobility, taking advantage of the natural overlap of the skyscraper typology. In his spatial model, traffic had three dimensions, attributing the third dimension to the displacement that would occur between the residential city and the commercial city, the first located above the second. Mobility was separated into several planes, similar to the American illustrations discussed above, which allocated the lowest level for vehicles and set a new zero level for the development of life in the plane shared by the residential and commercial city. A rigid network of bridges outlined that pedestrian plane, providing what Le Corbusier decided not to incorporate into his urban imagery. Hilberseimer’s images of the city seemed to find a replica in the drawings that the Mexican architect Francisco Mújica, fascinated by the city of skyscrapers and in tune with Corbett’s postulates, made after his trip to New York in 1926. Beyond the conviction that it had on the construction of the metropolis with pyramidal typologies close to the preHispanic temples, his drawing showed a city built on two well-differentiated levels: the lower one for road traffic and the upper one for pedestrians. The rigidity and orthogonality Figure 4: Hugh Ferriss. The Metropolis of Tomorrow, 1929 [6]. Figure 5: (A) Ludwig Hilberseimer. Vertical City, 1924 [7] and (B) Francisco Mújica. The City of the Future: Hundred Story City in Neo-American Style, 1929 [8]. 398 Adrián Martínez-Muñoz, Int. J. Transp. Dev. Integr., Vol. 5, No. 4 (2021) of his city zoned by height, entitledThe City of the Future: One Hundred Story City in NeoAmerican Style(Fig. 5) and published in his only bookThe History of the Skyscraperin 1929, is reminiscent of that Hilberseimerian Hochhausstadt. However, the most influential review of the spatial organization of mobility in a real vertical city context emerged, a decade after Hilberseimer’s cited work, with the construction of Rockefeller Center in Manhattan between 1931 and 1939. The dense network generated there, intertwining different programs at various levels, would once again mark the architectural debate just at the time when the Charter of Athens was being drafted. 4 SKYWAYS IN REAL CONTEXT Known as a ‘city within a city’, the Rockefeller Center (Fig. 6) was conceived as a reduced model of Manhattan itself in the middle of the Great Depression. The network of streets, by way of underground galleries, began a new way of understanding the city that unfolded below ground level, linking car parks, train stations, metro, offices, shops and squares in an exceptional complexity. It was the first time that a continuous pedestrian system was articulated between different volumes and users, generating a structure that increased the relationship with its urban context. Never before a network of ‘public tunnels’ had sewn together several blocks, resulting in a unitary fragment of the city within the city itself, in perfect harmony with it. Although the Rockefeller Center network, completed at the beginning of the World War II, failed to alter the destiny of cities, it generated such astonishment that in the years after the war, commercial networks began to emerge between skyscrapers throughout the American continent. Even though the Rockefeller network was developed underground, the concept could perfectly be transferred to an elevated level as a group of skyways. In fact, in 1956, a group of young architects influenced by Victor Gruen’s multilevel urbanism teachings proposed a network of high-rise pedestrian streets that was implemented in downtown St. Paul, the second largest city in the state of Minnesota. A year later, the architects of the University of Minnesota presented a similar plan for the centre of Minneapolis (Fig. 6), a neighbouring city. Separated by the Mississippi River, networks such as the elevated streets of Minneapolis and St. Paul differ fundamentally in the character of their management: private in the first case, public in the second one. The fabric of Minneapolis was built piecemeal through tradeoriented private investors. The first two bridges were built in 1962; later, the great Nicollet Mall increased the network in 1968; in the 1970s, with Philip Johnson’s IDS Center project (1972) (Fig. 6), much of the elevated street network was consolidated. Figure 6: (A) Rockefeller Centre New York, 1939 [9]; (B) P. Johnson and J. Burgee. IDS Center, Minneapolis, 1972 [10]; (C) Skywalks downtown Minneapolis [11]. Adrián Martínez-Muñoz, Int. J. Transp. Dev. Integr., Vol. 5, No. 4 (2021) 399 Today, the experience of Minneapolis, with more than 18 km of elevated streets (the longest in the world), has become a system on which investors depend if they want to succeed with their new skyscrapers. When a new skyscraper is planned in Minneapolis, the first issue to take into account is the connection with the network of skyways, with the target of getting the necessary flux of pedestrian, especially in the colder months when it is impossible to walk outside. The cases of Minneapolis and St. Paul were not the only ones that emerged in the American continent during those years. In Calgary (Canada), conceived by the architect Harold Hanen, another network of air-conditioned elevated streets that crossed skyscrapers was projected; this time as a unique project from the beginning of its creation. It was known asPlus 15since generally the bridges that crossed the towers were located at 15 feet, about 4.5 meters above the city ground floor. This plot connected several dozen buildings, including the most important shopping centres and shops in the downtown. The Calgary case was not a specific experience applied to a fragment of the city. On the contrary, it aspired to become a prototype of a vertical city where the network of elevated streets completed the total extension of the urban area. Throughout 1969, the still futuristic relationship between vehicular traffic and pedestrian traffic at an elevated level, appeared again in New York, with the recovery of the Second Regional Plan. This plan happened forty years after, and as a sequel to that of 1929. Under the title Urban Design Manhattan, and compiled by Rai Okamoto and Frank Williams, the second part of the Regional Plan concentrated its major advances in the identification of nodes scattered around the city where hybrid multi-level districts should be located as centres within the great centre: Grand Central Station, Times Square, Columbus Circle and Rockefeller Center, among others. This reformulation of the mobility and urbanism of the New York fabric culminated in the proposal of a new Office Cluster Model (Fig. 7), as one more node of the polycentric matrix, in the Greenwich Village area, west of midtown. This vertical complex condensed a group of office towers, with dwellings on the upper levels, crossed every ten floors by pedestrian bridges that provided some freedom of vertical and horizontal movement. The mobility system, through the access tree principle, added an extraordinary spatial complexity, without thereby impeding the correct functioning of road traffic at ground level. The efficient three-dimensional infrastructure, with a capacity for 120,000 workers, was in part indebted to the ideas defended years before by Stanley Tankel, in collaboration with Jane Jacobs, against the urbanism of Robert Moses. The main target of the Second Regional Plan of New York was not only to accommodate the high growth of population and propose a solution to the problem of traffic congestion of the metropolis, but also, to keep the scale and lifestyle of New York neighbourhoods such as Village, where Jane Jacobs lived. On the other side of the world, in Hong Kong (Fig. 7), one of the densest cities and with the greatest scarcity of ground on the planet, we can witness a labyrinthine three-dimensional landscape of elevated public roads drawn by the different daily flows: skywalks, underground passages, escalators and elevators. In the city of Hong Kong, there is not a conventional relationship between the levels of mobility, in part, forced by the sharp topography that acts as a background, and in part by the high population density. Hong Kong is today a city without ground – or with many overlapping grounds – in which one can move from one end of the city to the other without stepping on the ground established as ground zero. Elevated walkway systems now span the majority of the Sheung Wan, Central, Admiralty, and Wan Chai districts. The pedestrian network features a range of connector prototypes, including deckaccess plazas and podiums, flyover bridges, open-air footbridges, and high-bridge networks 400 Adrián Martínez-Muñoz, Int. J. Transp. Dev. Integr., Vol. 5, No. 4 (2021) (exterior pedestrian bridges over streets), interiorized walkways, elevated parks, and exterior escalators that scale the steep hillsides. In the book Cities without ground: a Hong Kong guidebook, authors write: ‘Urbanism in Hong Kong is a result of a combination of top-down planning and bottom-up solutions, a unique collaboration between pragmatic thinking and comprehensive masterplanning, played out in three-dimensional space. Footbridge networks throughout the city that grew piecemeal, built by different parties at different times to serve different immediate needs, eventually formed an extensive network and became a prevailing development model for the city´s large-scale urban projects’ [12]. Although the case of the High Line in New York was born with a different purpose than the aforementioned networks, it could be cited in this paper as a case that, from the contemporary vertical city point of view, proposes a linear infrastructure as an elevated urban park with great social success. The project repurposed the old and abandoned West Side Line of the railroad to transform it into almost 2.5 km of the landscaped promenade, stretching from the Meatpacking neighbourhood to the Hudson Rail Yards in Manhattan. In its linear development, it encompasses everything from stands for improvised shows, small squares and living areas to spaces for the exhibition of large-scale sculptures. The warp of the High Line, weaving together several skyscrapers at a certain height, is used by hundreds of New Yorkers every day to cross the west of the island from 30th Street to Gansevoort Street. Even though the project has a clear public vocation, like the rest of the streets and squares in the metropolis, it suffers from a strict time access restriction, probably due to security problems. If the High Line had been a real public infrastructure, open 24/7, we would have analysed it as a true skyway that helps humanize the vertical city. 5 FOUR CASE STUDIES WHERE MOBILITY IS DEVELOPED SEVERAL METERS ABOVE THE GROUND 5.1 Steven Holl, The Linked Hybrid, Beijing (China), 2009 With a kaleidoscopic dimension of ‘city within a city’, like that slogan that accompanied the Rockefeller Center, the Linked Hybrid project (Fig. 8) could well belong to a fragment of the aerial frameworks of Minneapolis, Calgary or Hong Kong. In the diagrams that explain Figure 7: (A) Second New York Regional Plan, 1969 [13]; (B) Hong Kong Skywalks (Picture by the author). Adrián Martínez-Muñoz, Int. J. Transp. Dev. Integr., Vol. 5, No. 4 (2021) 401 the gestation of the project, the city model that Steven Holl tried to make us understand was concentrated. It consisted of three small skylines of cities: the first showed a horizontal city of small buildings until 1980, the second exhibited a city of isolated and repeated monofunctional towers from 1980 and finally, the third (the Holl’s proposal) was drawn as a city of hybrid skyscrapers connected by skyways as a multilevel city. And this is the most interesting idea for this research: the elevated street that links the eight towers. The elevated street, with a variable width between five and fifteen meters, began at level twelve of the hotel tower at one end, and reached level eighteen on its way to the tower that encloses the site, leaving the ring unfinished. Holl placed program in these glass bridges or skybridges, including a gym, an art gallery, cafeterias, and even a swimming pool, with the added complexities that this implied structurally. The complex was intended to be a fragment of a self-sufficient city, hybridizing all kinds of uses between the volumes of the ground floors and the high street as a pedestrian system. Linked Hybrid thus housed a population of 2,500 inhabitants, aspiring to become an avant-garde prototype of the urban lifestyles of the 21st century. 5.2 ARC+RSP, The Pinnacle Duxton, Singapore, 2009 The City of Singapore is a pioneer in this kind of projects, among which is The Pinnacle Duxton (Fig. 8), built by ARC + RSP Architects in 2009. A vertical complex of 1,848 houses and 50 floors high that dreams of literally bringing the street and the plaza to the clouds, producing elevations of urban strata several meters from the Earth’s mass to create a multiground zero city. At The Pinnacle Duxton, the two trays aspire to reproduce outdoor spaces according to the tropical climate of Singapore: gardens for children’s games, spaces for barbecues, solariums, areas equipped for gymnastics and a running route of 800m in length, among others. Singapore is an architectural lab of this kind of buildings where a group of skyways offer public spaces in tallness, transferring squares and streets beyond the zero level. Between the most highlighted projects are The Interlace (2013) by OMA, SkyVille (2015) by WOHA architects or Sky Habitat (2016) by Safdie architects. 5.3 Chongqing city, China In search of those public circuits that intrude between towers, I found, during the summer of 2019, in The Guardian newspaper, within its Cities section, a review entitled Humans vs the city: the staggering scale of Chongqing in pictures (Fig. 9). The article showed an urban Figure 8: (A) Steven Holl, The Linked Hybrid, 2009 [14]; (B) ARC+RSP, The Pinnacle Duxton, Singapore, 2009 [15].