As a reminder, this is No. 10 in a series on the proposed north-south California High-Speed Rail system, which deserves national attention as the highest-stakes infrastructure project underway anywhere in America now. (Although someone from Philadelphia just wrote to say: Uncle! What we really need is HSR from the East Coast through to the Midwest. I know what he's talking about, but I'll leave that to someone else.) For previous installments see No. 1, No. 2, No. 3, No. 4, No. 5, No. 6, No. 7, No. 8, and No. 9.

The previous entry was very long and detailed—it was a reply by Dan Richard, the chairman of California's High-Speed Rail Authority, to an extensive set of criticisms. This one is short and thematic. It comes from a veteran of a Federal agency, and it concerns the larger question of how to think about projects that will take decades to unfold, and whose implications are by definition unknowable when the choice about whether to proceed, or not, is made. Let's turn it over to the former Federal administrator:

I am spurred to write by [a previous] post devoted to critics of HSR. I don’t know whether it’s a good idea or not, but I do have a long memory and an interest in technological innovation. Con Remember the super-sonic transport. In the 1960’s we knew all long flights would take place at supersonic speed. It was obvious, until it wasn’t.

Remember the ship the United States. In the 50’s we were very proud that the US had taken the trans-Atlantic speed record back from the Brits. The granddaughter of the designer is desperately trying to preserve the ship.

There’s always cost-overruns on big projects, always. Pro The HSR is building for the future, and the transportation and economic environment in which it will be tested will be quite different than today’s. For example, one disadvantage of rail and air is the hassle of renting a car on the other end. True enough today, but 20 years from now things like Uber and the driverless car may have made owning a car a rarity and renting a car the rule, which would impact the economics and convenience of HSR.

Simply acquiring the right of way may become significant in unexpected ways. The railroad magnates of the past didn’t realize that some of their rights of way would be used for fiber optic cable. And they didn’t realize they needed a bigger rail tunnel in Baltimore and a double-tracked tunnel in DC. Bottomline: The decision on HSR is going to shape the future in ways we can’t predict, and a touch of modesty in the arguments would be welcome.

I agree. What makes decisions like this important is that people will be living with their consequences a century from now. An overstatement? Everything about today's California life is conditioned by decisions about its freeway network made 60-plus years ago, and by the decision to tear up the Southern California light-rail network in the decades before that. Along the Eastern seaboard, in parts of the Midwest, and in the Plains, the U.S. rail network of the early 20th century has an obvious effect on where and how people live, work, and travel in the early 21st.

The long shadow of major infrastructure choices is also what makes such decisions difficult. We must choose among options whose consequences we can't fully anticipate. More on how we make such choices, still ahead.