The first phase of the Second Avenue subway cost $4.5 billion for just 2 miles, and took 10 years. The next 1.5 mile segment will cost $6 billion (that’s just the estimate) and take another 10 years. And that’s not even all that over budget or delayed.

I’ve never encountered a major public project in the US that was on budget and on time. I’m sure there are some, but that’s not the rule. Here in the DC area, we recently spent $150 million on a bus station (it’s a nice, 3 level bus station on existing public land). That was delayed and was $50 million over budget. The $6 million renovation project in the parking garage at the metro station nearest to me is years behind schedule. The purple line in Maryland is years late and billions over budget. The silver line in Virginia is years late and billions over budget.

Your “disaster” would be a miracle in a major US city. Such a miracle that few cities are even contemplating such things. DC, for example, is growing rapidly, and WMATA desperately needs another tunnel through downtown. And people are willing to spend that kind of money—WMATA just invested $6 billion and a decade constructing the silver line to Virginia. And Maryland is investing a similar amount in a light rail through the suburbs. But a downtown tunnel would be a $15+ billion, 20-year project here.