The Second Avenue Subway line was approved in 1929, but despite an overburdened public transit system, organisational and financial reasons kept it at bay until the early-21st century. Arup, in a design team joint venture, led full design and engineering services on the first phase of this project, as well as conceptual design and preliminary engineering work for all four phases of the project.

Arup took a total design approach to the tunnel construction, encompassing life safety issues, ventilation, material science and other factors to create a cost-effective and sustainable design. Our phase one design included four new subway stations, some of the largest underground excavations in North America, for which we used pedestrian modelling to simulate 3,000 different train arrival combinations and plan circulation patterns.

Arup’s work included less obvious, but important, aspects of subway planning, too, in an effort to make the passenger experience as pleasant as possible. Arup acousticians used recordings to model the environment and find solutions to the typical subway noise. Ultimately, all four phases will include 16 new underground stations; 8.5 miles of bored, cut-and-cover, and mined tunnels; tunnels crossing existing tunnels; the high-capacity system terminus; and an underground train storage facility.

Tunneling

Arup took a total design approach to the tunnel construction, one that encompassed life safety issues, ventilation systems, material science, and other factors to create a cost-effective and sustainable design. A tunnel-boring machine was employed to excavate the 12,800ft of twin-track tunnels in the first phase of the Second Avenue Subway. The four new stations on the line are some of the largest underground excavations in North America, ranging from 70ft to 90ft in width and up to 1,300ft in length. Adding to the complexity of the job, these mined caverns all have escalator and elevator connections to street level—features much appreciated by riders who have long endured stairway-only access.

Graphic showing the tunnel design for Second Avenue Subway
The new stations include both escalator and elevator connections to street level as opposed to stairway-only access.
The canopy entrance to 96th Street Station is lit with bright blue LEDs to guide riders into the station.
The canopy entrance to 96th Street Station is lit with bright blue LEDs to guide riders into the station.
Interior view of one of the stations. Credit: Charles Aydlett courtesy AECOM Arup JV
Pedestrian modelling techniques helped determine the location of escalators, stairs and elevators.

Pedestrian Modelling

In the absence of a robust set of design guidelines for a new, modern subway line, the AECOM-Arup team worked with NYCT Operations Planning to set out design parameters and performance metrics. Using a newly developed model to simulate 3,000 uptown and downtown train arrival combinations, the team generated dynamic pedestrian model simulations for all stations for the AM peak hour. These simulations were used as a design tool to inform the optimal circulation provision for moving passengers between trains and the outside street level, even taking into account the complex movement patterns associated with transfer passengers at interchange stations and the challenges at 72nd and 63rd street where abnormally deep stations necessitate increased use of elevator access.

pedestrian modelling, combined with community consultation, helped to determine the location of sidewalk infrastructure
Pedestrian modelling, combined with community consultation, helped to determine the location of sidewalk infrastructure

Acoustics

Working with recordings taken at existing subway stations, Arup’s acousticians used the firm’s SoundLab technology to create digital models of the environment and determine the best way to quiet the bone-rattling noise typically found in the subway. The solutions include joint-free train tracks with ties that are encased in concrete-covered rubber, ceilings lined with perforated metal panels that are backed with sound-absorbing fiberglass (instead of the echo-prone tile and stone used in other parts of the transit system), and new, carefully-oriented public-address speakers as part of a complete audio system that is optimized for intelligibility.

On the platform at 96th Street Station, the noise-absorbing panels made from ceramic, metal and fibreglass are clearly visible, inset into the wall.
On the platform at 96th Street Station, the noise-absorbing panels made from ceramic, metal and fibreglass are clearly visible, inset into the wall.