[fdr]

That’s right. System refreshes are a fact of life, especially if one is parsimonious in using what works until obsolescence. There are downsides of doing things that way, but I don’t see it inherently more defective than other approaches, such as some kind of continuous refresh that has a conceit of keeping a system “modern” in perpetuity.

[thsksbd]

But twenty years for a train seems very low. My daily driver is 12 years old, I thrash it every morning and never gives me problems. I live in the snowbelt.

By comparison a train is vastly over-engineered and has an electric drive train. Sure stuff will need replacing but a train should last 40 years at least

[fdr]

I wouldn't call myself as particular on train maintenance...but consider that these trains are run more or less continuously. You thrash your car in seasonally tough conditions every morning, but these drive all day and most of the night. So, I'm not sure if the comparison is apt on these grounds.

A cursory search suggests that quite a few manufacturers design for light rail car lifetimes of 25-30 years, not forty. These tend to be of European origin, which tracks San Francisco switching from an Italian to a German vendor. I don't see evidence that it's a common practice to significantly extend the tenure of those devices there nor here.

Funnily enough, I see no problems with the Breda trains personally as a passenger. But once they've shaken out the major bugs, the Siemens train reliability is anticipated to be triple or more. It may not make sense to design a traincar for a fifty year term.

[inferiorhuman]

Transit vehicles purchased with federal funds are required to meet a minimum service life (see below). For the Muni Metro you're looking at a minimum expected life of 31 years.

https://www.transit.dot.gov/sites/fta.dot.gov/files/2021-11/...

[fdr]

That's an average service life from what I can tell, not a minimum (a minimum average?). But yes, it does trend a tad higher than what my cursory search indicated (25-30, feds want 31)

Looks like this has been the subject of some industry wandering in the last generation:

https://www.urban-transport-magazine.com/en/new-boom-in-the-...

Some were planned for 30-35 years, some for 25 to 30, some models have aged so gracefully they may be refurbished, yet others may have been engineered with roughly the correct obsolescence window in mind as engineering has advanced in the last generation, even in the dimensions of making some things simpler and more reliable (one of the billed advantages of some of the Siemens train mechanisms).

[inferiorhuman]

  FTA has set a default ULB as the expected service years for each vehicle
  class in the table below. … In cases where the submitted ULB differs
  significantly from the default value, agencies may be prompted to submit
  justification.

The first generation of modern streetcars (the Boeing-Vertol) barely made it 24 years and that was scandalous. The next generation (Breda) were so bad that their manufacturer was banned from city contracts. Even so the Boeing cars were retired post haste as Muni took deliveries of the Breda cars. The last of the Boeings were decommissioned in 2001, and the Bredas look like they'll be around the full 31 years at least.

Basically if you're buying things that don't last 30 years, the feds are going to be very reluctant to give you money.

[jcgrillo]

https://www.wbur.org/morningedition/2016/03/07/mbta-signal-m...