Solihull-based Arup is being retained in a joint venture by New York City Transit to provide all preliminary engineering services for an eight-mile subway line beneath Second Avenue in Manhattan.
The line was originally proposed in 1929 and work did start in the early 1970s but was halted in 1975 when New York City hit a financial crisis.
In March this year, a $337 million (£172 million) contract was awarded to a consortium to start digging a tunnel that will extend from 63rd Street to 96th Street and provide two shafts for a station at 72nd Street.
Arup is working on the project with AECOM, one of the largest US-based engineering design firms and the parent of Faber Maunsell. Arup says it was chosen in recognition of its light and airy designs of new underground stations in cities such as Hong Kong and Singapore.
Don Phillips, Arup's project director in New York, said the project was complicated because the varying geology of Manhattan meant the subway would pass through rock and soft ground.
"The complex interaction between the existing infrastructure, buildings and the subway is a particularly challenging and crucial element of the project," he said.
The first $3.8 billion (£1.93 billion) phase will be used by an estimated 191,000 passengers daily once it is complete in 2013.
Three other phases will follow, and when the subway is finished in 2020, the twin-track line will run the entire length of Manhattan and will include 16 underground stations.