People can want estimates and deadlines, but the estimates won’t be correct and the deadlines won’t be met for an ambitious custom build house, a subway tunnel

People can want estimates and deadlines, but the estimates won’t be correct and the deadlines won’t be met for an ambitious custom build house, a subway tunnel through unknown “legacy,” or a diagnosis and treatment of an exotic disease, because that’s not how it works. They might be correct for overpass #10,000, build #300 of Standard House Model B, or churning out antibiotic prescriptions. But those projects should cease to require much if any engineering support, leaving only the ones with more unknowns. Subway tunneling is a really great example. You run into underground infrastructure that wasn’t in the documentation and you have to stop and figure out whether it’s still used, what it’s connected to, etc. and either refactor it out of your way or change your own route before continuing. You don’t know in advance how many such situations you’ll run into or how difficult they’ll be to untangle. So subway projects are chronically late and over budget.