How do you revitalise a historic city centre through design and public artwork?

Arup joined the project as the lighting designers to address the transition of Centre Square as day turns to night. Dilworth Park, sitting beneath the grandeur of City Hall, is softly illuminated with adjustable spots mounted high on a display of poles. The distinctive glass entrances ease people through a transition between night sky and underground station. Integrated handrail lighting provides a warm glow to the entrances and keeps the glasswork clear of additive elements. In the transit station below, Arup identified key opportunities where lighting would enhance the feeling of safety and security — in a comfortable and architecturally integrated manner. Linear lighting is arrayed in a horizontal display across the ceiling to break-up the long connecting hallways, while additional layers of downlighting address kiosk and transaction stations.

Centre Square has always played an important role in Philadelphia’s history, from its early days as the site of a water pump station, one of the city’s first major public works projects that enable the citizens to thrive, to the beginnings of the Pennsylvania railroad when the former pump site became an integral station in the interstate line. In the 1950s, the suburbs we know today experienced an influx of former city-dwellers and Broad Street Station and the Pennsylvania Railroad struggled to remain relevant with new and improved electric-lines that made stops throughout the suburbs. The station closed its doors, and Centre Square fell silent. 

When Arup was brought on to design the lighting for Dilworth Park, it was more than a city amenities project — Centre Square needed serious reform and regeneration that would honour its history and reinstate the important active public space. The park opened in 2014 and was an instant success; the green space continues to hold programs day-in and day-out, the splash fountain is alive with laughing children, and the adjacent café is an oasis for a mid-day lunch or evening snack. Workout classes spread across the landscape, and evenings are filled with notes of live jazz flowing from assembled stages. 

The final piece in the park’s puzzle came to fruition in 2018 when Janet Echelman’s art piece, Pulse, opened. The piece, which was designed not as an installation within the park but as an integral part of the park itself, is a tribute to the historic presence of water and transportation at Centre Square, while embracing the impact of modern technology. Pulling transit data collected from the station below, Pulse uses this as the trigger for what happens above ground. A line of fog, creating a stunning wall that blasts into the surrounding landscape, is seen racing across Dilworth Park. The line traces the path of the subway — the green line in particular — which has been chosen for phase one of Pulse. The following phases will cover the remainder of the subway lines that commute to and from City Hall.

Arup's lighting team worked closely with each collaborator to understand the physics and materiality of the fog. Light follows the fog as it moves along the line, using linear LEDs below that correspond to the colour of the train line. Layers of light above the fog, from fixtures mounted to the existing light poles, add dimensionality and character to further animate the particles. Finally, there are gobos — theatrical fixtures that provide patterning and texture. The result is a spectacle of colour and mist, calling passers-by of all ages to pause for a minute and experience the dynamics of the city.