https://www.nytimes.com/2017/12/28/nyregion/new-york-subway-...

There are “nippers” to watch material being moved around and “hog house tenders” to supervise the break room. Each crane must have an “oiler,” a relic of a time when they needed frequent lubrication. Standby electricians and plumbers are to be on hand at all times, as is at least one “master mechanic.” Generators and elevators must have their own operators, even though they are automatic. An extra person is required to be present for all concrete pumping, steam fitting, sheet metal work and other tasks.

In New York, “underground construction employs approximately four times the number of personnel as in similar jobs in Asia, Australia, or Europe,” according to an internal report by Arup, a consulting firm that worked on the Second Avenue subway and many similar projects around the world.