All the Sidewalk’s a Stage: 4th Street SW Underpass Enhancement, Calgary, Alberta

MBAC transforms a dreary Calgary underpass into a colourful, interactive installation that mirrors the movement of pedestrians on its screens.

A responsive LED wall system is programmed to mirror the movement of pedestrians travelling through the renovated 4th Street Underpass, at the southern edge of downtown Calgary.

PROJECT 4th Street SW Underpass Enhancement, Calgary, Alberta

ARCHITECT the marc boutin architectural collaborative inc.

TEXT Ximena Gonzalez

PHOTOS Yellow Camera

When the economic downturn hit Calgary in 2014, offices and businesses vacated the city’s downtown core. Today, with the added impact of the pandemic, nearly 30 percent of office space remains vacant. But a program started when the city was booming is helping hold up spirits and support future investment in Calgary’s business district.

Launched in 2010, the Centre City Underpass Enhancement program set out to improve the pedestrian experience at each of the eight railway underpasses joining downtown Calgary to the Beltline neighbourhood to the south. These underpasses were originally designed to overcome the ground-level barrier created by the CP rail line at the southern edge of the core, and move cars in and out of downtown. Little thought was given to people moving on foot, who were funneled along narrow sidewalks at the edges of the underpasses.

Location plan

A decade ago—with a thriving economy and thousands of pedestrians using the underpasses on a daily basis—the possibilities for improving these infrastructural links seemed endless. “The Centre City is the economic engine of Calgary,” reads the Downtown Underpass Urban Design Guidelines. Now, projects like the underpass enhancement program remain equally important, providing a solid foundation for recovery. 

Designed by MTa and completed in 2016, the 8th Street SW underpass was the first of these enhancements. That was followed by 1st Street SW, designed by the marc boutin architecture collaborative (MBAC) and completed in 2019. MBAC is also responsible for the latest of the series, the underpass at 4th Street SW, completed at the end of 2019.“The [4th Street SW] project started when the city had decent budgets,” says architect Marc Boutin, whose firm was awarded the 1st Street commission in 2012 and the 4th Street commission in 2015. “[Then] all of a sudden, the economy crashed.”

But despite budget changes, the design team delivered a space that is more than a safe connector. The 4th Street underpass functions as a poetic catalyst for an embodied experience, facilitating a conversation between people and place.

In the central area of the underpass, the walls are topped by sculpted polycarbonate veils that capture and reflect light.

As pedestrians reach the start of a gentle downward slope at either end of the underpass, a sense of anticipation is created by the glowing lights of the installation ahead, as if one were to enter a stage. Then, as each user moves through the space, a digital avatar appears across the street at the opposite end of the underpass, travelling in sync to meet the participant at the middle of the space. In the central stretch, which is open to the sky, the walls are crowned by polycarbonate veils that capture and reflect colour and light. Mirroring the movements of pedestrians, the digital display nudges pedestrians to realize that they are more than mere observers in the urban realm: they are active participants.

“In some ways, this space is a public manifestation of the self into the idea of spectacle, and into the idea of a conversation at the scale of the city,” Boutin says. “And it is a physical one, as opposed to an immaterial one.” 

This experience is facilitated by a design that seamlessly integrates public art, pedestrian needs, and City maintenance requirements.

MBAC’s design for the underpass, completed in collaboration with visual artist Krzysztof Wodiczko, began by observing pedestrians using the existing sidewalks. The designers identified the opportunity to create an interactive installation that would allow for active engagement with the space of the underpass. “It was a building of the narrative around body, space, and conversation,” Boutin says.

Assembly diagram

Supported by INVIVIA, a design consultancy and technology research company based in Cambridge, Massachusetts, Wodiczko developed a responsive public art installation to capture the movements of pedestrians. Four 360-degree cameras are carefully concealed on the columns that support the road and rail line: two towards each end, and two near the middle.

The video captured by these cameras is processed through custom software developed by INVIVIA, which controls the lighting system and generates the pedestrian silhouettes that move along the responsive media wall.

Constructed with translucent polycarbonate panels, the responsive wall extends along the east and west sides of the underpass—stretching along the 800- and 900-block on 4th Street SW, this underpass is longer than the others. The panels act as a light-diffusing surface for the LED lights behind. This system shares similarities to the design for the 1st Street underpass, which includes a two-layered skin with supergraphics of rolling prairie grassland and soaring mountains overlaid by a perforated aluminum screen. For 4th Street SW, the designers introduced light as the key graphic element.

Designed for durability and ease of maintenance, the wall panels include an aluminum exoskeleton, a layer of laminated safety glass with a translucent interlayer for light diffusion, a translucent polycarbonate panel that holds the LEDs, and a supporting galvanized steel subframe.

With 1st Street, the MBAC team experienced the challenges inherent to redesigning a public space of this kind, including accounting for vandalism and maintenance. To protect the media wall, they decided to locate the assembly’s structural aluminum ribs on the outer surface. The exposed aluminum ribs were sculpted to catch and reflect the light of the LED fixtures. “We needed to make sure it didn’t look like a jail,” Boutin notes. Furthermore, for ease of maintenance, the wall is designed so that a single person can detach the aluminum ribs to clean the glass, and remove individual panels to change the LED lights.

Despite Calgary’s changing economic climate, the design team succeeded at transforming a dingy underpass into an interactive display—part public space and part public art—that improves the experience of all pedestrians. “We knew that part of the success of the project would hinge on how integrated it was,” Boutin says. “The project is a piece of urban infrastructure, it’s a piece of streetscape, and it’s a piece of public art.”

In a struggling downtown, MBAC’s public realm work helps keep Calgarians hopeful for the future. A new downtown strategy, aiming to attract talent and investment, is currently in the works. A draft of the plan, titled A Roadmap to Reinvention, describes downtown Calgary as “a resilient and vibrant place for everyone, with welcoming neighbourhoods, active streets, and well-used public spaces.” Multi-functional projects like the 4th Street SW underpass lay a solid foundation for this vision to materialize.

Ximena Gonzalez is a Calgary-based writer and editor with an educational background in architecture and environmental design.

CLIENT The City of Calgary | ARCHITECT TEAM Marc Boutin (FRAIC), Nathaniel Wagenaar, Trevor Steckly, Jodi James, Sean Knight, Ryan Agrey, Michelle Smith Cowman | STRUCTURAL Entuitive Engineering | MECHANICAL Reinbold Engineering | LIGHTING/ELECTRICAL Nemetz (S/A) & Associates Ltd / SMP Engineering | CONTRACTOR Pomerleau | PUBLIC ARTIST Krzysztof Wodiczko and Allen Sayegh / INVIVIA | BUDGET $6.7 M | COMPLETION Winter 2019