how were they modernized?
UNANSWERABLE
when was the subway built in new york In 1904 which methods were used for construction? Different methods were used such as cut-and-cover being one of them
wiki:19918500
New York City Subway [SEP] Construction methods
When the IRT subway debuted in 1904, the typical tunnel construction method was cut-and-cover. The street was torn up to dig the tunnel below before being rebuilt from above. Traffic on the street above would be interrupted due to the digging up of the street. Temporary steel and wooden bridges carried surface traffic above the construction. Contractors in this type of construction faced many obstacles, both natural and man-made. They had to deal with rock formations and groundwater, which required pumps. Twelve miles of sewers, as well as water and gas mains, electric conduits, and steam pipes had to be rerouted.