The Almondsbury Interchange, booklet cover, published to mark the opening of the interchange in 1966. Freeman, Fox and Partners.

lthough there was no official celebration, 8th September 2016 marked the 50th anniversary of an event of national significance in Britain. Slightly north of Bristol, the largest city in south west England, is the Almondsbury Four-level Stack motorway interchange. When completed in 1966, this work of urban infrastructure was deemed so significant that it was officially opened by Her Majesty the Queen. Barbara Castle, the Labour transport minister of the time, declared it one of the “cathedrals of the modern world” (Harrison, 2011). Half a century later, despite the endurance of the structure, it seems to have been quietly forgotten. 

A type of “Omni-Directional Four-Way Interchange” (Williams, 1975: 13), the Four-level Stack is a road junction that allows traffic travelling from any direction to change to any other direction without stopping or significantly slowing down. Unlike other types of common motorway interchange, such as a Roundabout or a Cloverleaf Interchange, the Four-level Stack is designed to minimize the loss of speed by avoiding tight corners or junctions where traffic must stop in order to give way. The goal is to enable traffic to change direction from any point while eliminating deceleration, creating for each driver/car a smooth transition to a new course of travel in seemingly frictionless motion. To do so, four levels of traffic must cross at a central point, enabled by a series of elevated roadways — something JG Ballard likened to “copulating giants” in his novel Crash (1995 [1973]: 76).

M4 / M25 Interchange, London, UK, (2016). © Ilana Mitchell and Peter Merrington

These interchanges inevitably create differential mobilities — on the one hand enabling the movement of individual drivers, and on the other creating material barriers, cutting through communities or creating hard edges in the city or landscape. On paper and from the sky the Four-level Stack is a graceful swirling form, a perfect switch, neatly and smoothly offering new paths in all directions: dreamlike, futuristic and other-worldly. From the tarmac, on the road, it can be obscure, even hard to see, and, at speed, confusing and panic-inducing. From the sidelines on the ground its obstructive physicality is unmissable - a permanently grounded monument to intangible speed and travel. By creating smooth, frictionless paths through space, such interchanges offer the sense of a “homogeneous experience”, limiting connections to the locale being passed through or over (Easterling, 1999: 77).

Aerial view of a freeway interchange in Los Angeles, (No date). © California Historical Society Collection 1860-1960 at the University of Southern California Libraries.

Almondsbury was the first Four-level Stack to be built in the UK. First designed and built in Los Angeles in the 1940s and 50s, these interchanges have slowly spread across the globe, bringing together contested social, political, and environmental concerns. Here are entwining stories of expanded car dependency, the power of carbon capital, polluted air, infrastructure imposition, individualism and expensive prestige state projects. 

Almondsbury Interchange, Bristol, UK, screenshot, (2021). © Google Earth.

Despite their collective and individual significance, it is perhaps unsurprising that there was no interest in celebrating the 50th anniversary of the Almondsbury interchange. The Four-level Stack as an individual entity is little considered outside of a small number of specific contexts, primarily civil engineering and Los Angeles urban heritage, as well as by those who live in their shadows.

Over the last few years, we have been exploring and documenting their occurrence across the globe through an arts research project - tracing the history of the stack while also responding to them in creative ways. As part of the background of urban landscape they can be easy to ignore, but once we started paying attention, we began to find representations of them appearing in many different - and sometimes surprising - contexts; the homepage of  Society and Space for one, where circling drone footage depicts a Four-level Stack in central Shanghai.

In this illustrated essay we trace a short visual history of Four-level Stacks over the last seven decades, from their early presentation as celebrated engineering marvels; to contested sites of exclusion, subjugation, protest and resistance; to their symbolic role in film and television and as a signifier of urban complexity and machine intelligence. As with the interchanges themselves, the way images of them are used are often contested and contradictory.

Aerial view of four level interchange of Arroyo Seco Parkway (Pasadena Freeway) and Highway 101, looking North East, Los Angeles, California, USA, (No date). © The Historic American Buildings Survey (HABS), Historic American Engineering Record (HAER) or Historic American Landscapes Survey (HALS), Library of Congress Prints and Photographs Division Washington.

Conception and celebration

The concept for the Four-level Stack is attributed to WH Irish, an engineer with the California Division of Highways in the 1940s (Berg, 2015). The first version, now called the Bill Keene Memorial Interchange, fully opened in 1953 in Los Angeles, connecting US Route 101 and Route 110. Though there are now over a hundred stacks worldwide - and their number is slowly increasing - Los Angeles is the only place in the world where they have any kind of heritage status, aided by the energetic work of architectural critic Reyner Banham (1971), with later editions of his book Los Angeles: The Architecture of Four Ecologies, featuring an image of a Four-level Stack on the cover. In LA, their birthdays are celebrated, and sometimes the interchanges of LA are held up as icons of the city in the same way as the Hollywood sign. As Eric Avila (2014: 132-135) notes, the artist James Doolin spent a week camping at the interchange of the I110 and I5 before making one of his hyperreal paintings Bridges in 1989. In 1995, the LA Metropolitan Transportation Authority commissioned Doolin to create four murals for its headquarters. These paintings depict the development of the city since 1870 - skyscape images that showcase how the city was built up and formed around its transport systems, of which the Four-level Stacks are a prominent feature.

James Doolin, Bridges, 1989. Oil on linen, 72 x 102 in. (183 x 259 cm). Courtesy of the Autry Museum of the American West and Lauren Doolin McMillen.

By far the largest proportion of Four-level-Stacks are in the United States, where many were built as part of the extensive and contested post-war national interstate freeway development. Outside of the US, few countries have more than one. The UK has three in southern England, two at junctions on the M25, the circular motorway that rings London, and at Almondsbury. Individual constructions exist in diverse international cities such as Athens, Caracas, Durban, Madrid and Sydney. Increasingly they are being built in the global south; in China there are multiple stacks in Guangdong Province and in Shanghai, in Ghana the Pokuase Interchange was completed in 2021 and a new Four-level Stack is being built in Delhi, India

The earliest Four-level Stacks were celebrated as modernist masterpieces — the pinnacle of infrastructure design, concrete engineering and industrial ingenuity on a grand scale. Charles and Ray Eames’ film installation Glimpses of the USA, shown at the American National Exhibition in Moscow 1959, depicts modern American life through a set of still images projected onto seven large screens and in a theatre designed by Buckminster Fuller. Glimpses of the USA’s images of different freeway interchanges, including the Four-level Stack, encapsulated these celebratory representations — and brought civic engineering and the Four-level Stack, as a bombastic modernist design conception, into the US’ Cold War soft-power efforts. Such cultural diplomacy was a tool used to challenge the Soviet Communist regime by exporting images of consumer goods, such as shiny kitchen gadgets and American car culture. The domination of the automobile - culturally, economically and architecturally - within developing US cities was presented as aspirational, a futuristic sense of freedom (Yarrow, 2009). Of course, as Easterling (1999: 76) notes, “For all the claims of pioneering individualism… the interstate was one of the most centrally controlled and bureaucratically directed chapters in American history” - as the building of such large infrastructure generally requires the mobilization of substantial public resources and political will.

Writing about LA freeways in 1989, Jean Baudrillard (1989: 52-53) characterized the dominance of car culture in the city as: “A total collective act, staged by the entire population, twenty-four hours a day.” This creates a transformed sense of space and movement, “a milieu into which you insert yourself gently, which you switch over to as you might switch over to a TV channel... All this creates a new experience of space, and, at the same time, a new experience of the whole social system.” Here this new sense of driving space is experienced as a fluid media environment, something Margaret Morse (1998: 99) also compares to the “fiction effect” of watching television, enabling a “partial loss of touch with the here-and-now”.

In 1996, James Doolin was commissioned to paint four murals by Los Angeles County Metropolitan Transportation Authority (Metro) for their headquarters that showcase the city’s changing landscapes and evolving transportation systems through the decades and into the future. This image, Los Angeles Circa 1960, includes one of LA’s Four-level Stacks. Credit: Metro Headquarters, Los Angeles Circa 1960, James Doolin, artist. Courtesy of Los Angeles County Metropolitan Transportation Authority (Metro) and Lauren Doolin McMillen.

In a related sense, the Four-level Stack could be thought of as another successful export from LA, just as the films made in Hollywood reach around the globe. Though, of course, outside the USA, most people are more likely to encounter a Four-level Stack through media representations than to ever drive through one.

On the big and small screen

You see them everywhere you look, and I dont know why Ive never thought of it before, but one day I just started wondering, where are all those highways heading?” Cozy (River of Grass, 1994, dir Kelly Reichardt)

Four-level Stacks feature as urban backdrops and spectacular event spaces in many films and television programs, often in association with LA but also other US cities. Just after its completion, the Bill Keene Memorial Interchange was showcased in the 1953 Hollywood epic War of the Worlds, as the population of LA fled an incoming alien invasion (Ethington, 2001).

The most iconic appearance of a Four-level Stack on film is perhaps the miraculous bus jump over a gap of the unfinished I110 and I105 LA freeway interchange in the 1994 action film Speed. More recently, the same interchange became the stage for the opening scene of the 2016 musical La La Land. Overhead zoomed-out footage is a staple of urban TV drama, and Four-level Stacks frequently appear in transitions between scenes; in True Detective Season 2, a Stack features in the opening credits, part of a montage that evokes a sense of urban alienation.

Still image from River of Grass, dir Kelly Reichardt, 1994. Courtesy of Oscilloscope Laboratories.

More poetic representations question environmental destruction, as in film director Kelly Reichardt’s 1994 feature River of Grass. Here the site of a newly built Stack that encroaches on the Florida Everglades becomes the backdrop to a key scene in the film. The metaphorical crossroads in the protagonist's story is symbolically played out at the literal crossroads of the Four-level Stack.

Urban photography

While they are popular mise-en-scène, the Four-level Stack also takes a more forward role as protagonist in a particular type of urban photography. Their formal structural beauty has been celebrated in the work of American landscape photographer Ansel Adams, who aligned their form with the roots of an ancient tree. 

Catherine Opie, Untitled #23 from "Freeway" series, 1994, platinum print, artwork dimensions: 5.7 x 17.1 cm. 2 1/4 x 6 3/4 in. © Catherine Opie. Courtesy the artist, Regen Projects, Los Angeles and Thomas Dane Gallery.

They become monumental sculptural forms in their own right in Catherine Opie’s Freeway series. By photographing them very early in the morning, Opie intentionally avoids people and cars, stripping the roads of their sense of functionality and emphasizing the form of the structure over their utility or location. Opie sees a connection in these works with the scale and monumentality in Maxime Du Camp’s mid-nineteenth century photographs of the Egyptian pyramids.

Expanding on this theme, a number of photographers have sought to depict the Four-level Stack in the form of epic post-human, aerial landscapes - often devoid of visible people, they showcase our simultaneously grand and monstrous actions. This can be seen in the work of artists such as Edward Burtynsky and Andreas Gursky, as well as, often anonymous, Instagram accounts that regularly display images of the Four-level Stack as aerial spectacles of the industrial sublime (see Schuster, 2013).

Shutterstock image titled ‘Aerial view of a massive highway intersection in Los Angeles’, (No date). © TierneyMJ / Shutterstock.

Both celebratory and sinister, such images are often enabled through the somewhat dead eyes of a drone - in a sense mirroring the god’s-eye-view perspective of early war photography and raising questions about the power relation at play that are enabled through the view from above (Amad 2012; Kaplan, 2017).

Stock images and artificial intelligence 

Advert at Paris Charles de Gaulle Airport, (2016). © Ilana Mitchell and Peter Merrington.] 

Aerial photographs of Four-level Stacks have also found another meaning in a new context. Increasingly, we have found aerial images of the Four-level Stacks being used as a visual shorthand in adverts, reports, documentaries and news features to represent or signify a sense of contemporary urban complexity, often linked to the advance of new technology. We have also found them being used to embellish work on automation, algorithms and artificial intelligence: free-flowing cars on the interchanges stand in as a kind of visual shorthand for computerized agency, often with reference to self-driving cars.

Examples include the cover image of a report titled the Ethical and societal implications of algorithms, data, and artificial intelligence: a roadmap for research, this Wall Street Journal video Coronavirus Pandemic Fuels Chinas Self-Driving Cars, Tech Crunch articles about machine-to-machine technology and the Internet of Things, or international business conferences, such as this 2018 event called Shaping The Future. In many cases these are stock images, intended to be abstracted from their original location and used to present a kind of urban everywhere, rather than the specific locus they represent.

Shutterstock stock image titled 'SHANGHAI - Night skyline view of city and highways with flowing traffic’, (2013). © Peter Stuckings / Shutterstock.

Politics, protest, place and community

Over the history of the Four-level Stack, the power and capital, both political and financial, required to build such large pieces of urban infrastructure has pitted these concrete giants against those whose voices have been least heard or willfully ignored by those in power. 

Little Italy Killed By Progress', View of protestors at a demonstration against the proposed 'Lower Manhattan Expressway,' New York, New York, August 23, 1962. © Fred W. McDarrah/MUUS Collection via Getty Images.

In the US, the construction of these freeways divided, displaced and destroyed communities, but not necessarily indiscriminately: planning often routed through areas of designated as ‘blight,’ destroying communities of color in favor of connecting White suburbs and cities (Avila, 2014). And even the protests fell along racial lines - as just one of many possible examples shows, protests in Southern California in the 1960s by residents of White neighborhoods succeeded in the rerouting of the Santa Monica Freeway through Black and Chicanx areas, displacing 15,000 residents (Davies and Wiener, 2020). Freedom of smooth movement for some, enforced displacement for others.

Appealing to their status as engineering achievements often lends a kind of implied political and social neutrality to these structures - but Four-level Stacks, and the freeways they connect, are far from apolitical. The ongoing utility to those who move through them on a daily basis is often in stark contrast to those living in their proximity. As Meredith Drake Reitan writes (2011: 165), Peter Hales saw artists as complicit in this process, as: “grand-style photography presented an orderly, civilized city free of slums, restless laborers, and the chaos of laissez faire capitalism… [where] elites were encouraged to imagine a city that could be understood as a whole entity… [which was] only possible through the artful and deliberate exclusion of other vistas”.

In Our Path, #45, © Jeff Gates 1993-2022.

There are many art projects, though, that connect to deeper social and political dimensions. Jeff Gates’ In Our Path documents the demolition of a neighborhood to make way for the building of the Century Freeway Corridor in Los Angeles. Carlos Almaraz lived right by the Hollywood Freeway, and would be woken at night to the sounds of high speed car crashes, which he depicted in his paintings.

Dana Lixenberg
Freeway, 1993
From the series Imperial Courts, 1993-2015
© Dana Lixenberg
Courtesy of the artist and GRIMM Amsterdam | New York. 

Over 22 years, Dana Lixenberg made Imperial Courts 1993-2015, documenting a social housing project built in 1944 near the Imperial Highway in Watts, Los Angeles that attracted predominantly Black migrants from the southern states. Frustration at police brutality, racial discrimination and social isolation led to the Watts riots of 1965 - and then the Rodney King riots of 1992. Over this time, Imperial Courts has sat in the shadow of the nearby stacked bridges of the freeway interchange - just one of many communities displaced by, or relocated to live by, these spaces created for others to speed past.

Dana Lixenberg
Diamond with Felia and Sheena, 2015
From the series Imperial Courts, 1993-2015
© Dana Lixenberg
Courtesy of the artist and GRIMM Amsterdam | New York. 

In 1970, residents of Barrio Logan in downtown San Diego successfully demonstrated to turn the land under the San Diego-Coronado Bridge (a half stack!) into Chicano Park - a central community space that continues to thrive. Lincoln Park is a similar artist and community led project in El Paso, under the 4-level mess of a junction known locally as the Spaghetti Bowl. 

San Diego Street Journal front page showing the first day of the Chicano Park takeover, (1970). LesThePhotog, Shared under CC BY-SA 4.0 License.

These Chicanx communities may not have succeeded in protesting the building of the freeways, but they continued to protest, and were able to reclaim some ownership, and stamp a sense of cultural identity, on to the accidental architecture the imposed concrete created. As Avila (2014: 178) notes “the voices of dissent and invocations of racial pride have been tattooed on the skin of public infrastructure.”

Mural in Chicano Park, San Diego that reads ‘All the way to the Bay’, (2012). Rpotance, Shared under CC BY-SA 4.0 License.

These kinds of projects affirm the stacks themselves as more than engineered objects, they are social spaces, lived spaces, filled with community, art and activism. Tracing the cultural and visual uses of the Four-level Stack shows some of the inherent contradictions in attempting to understand these structures as both structural forms and places. As Ethington (2001: 29) writes on the modernist landmarks that are the Four-level Stacks in Los Angeles, they are part of a “complex space-time fabric where the present, the past, the near, and the far can be made visible or invisible”.

Unlike the raised towering pillars of the interchange bridges synonymous with LA, if you approach Almondsbury interchange on foot you will find it sunk into green pasture. Edged with wildflower meadows. Just a few tall thin, streetlights rising above the trees. You can hear it. It is in the air, but you cannot see it.

M4 / M25 Interchange, London, UK, (2018). © Ilana Mitchell and Peter Merrington.

Four-level Stacks are spectacular and mundane, gigantic, and contradictory. It is perhaps therefore not a surprise that these interchanges have been both exalted and condemned. Utopian in design and technical aspiration, dystopian in their ecological impact and the social implications of their imposition upon communities. Over 80 years, the breadth of ways they have been represented speaks to these stark contradictions. Once they stop becoming useful, will they crumble or become monuments?


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Ilana Mitchell: artist-researcher, curator, project facilitator and advisor. She is Artistic Director of Wunderbar, Chair of The NewBridge Project, and was a founding member of the Star and Shadow Cinema, all based in Newcastle upon Tyne, UK. 

Peter Merrington: interdisciplinary researcher, writer and creative producer. He is a Lecturer in the Business of the Creative and Cultural Industries at the University of York, UK.