It would just save emissions not money. Is Berlin afraid to invest in any big projects with a bit of risk, because they’re still traumatized by the airport debacle, that took about a decade more to finish?! Correct me if you’re ein Berliner. Taking a bit longer is normal in big infrastructure projects but years is something different.
Reddit had a good run for over a decade, but as always with the internet, now a better thing will take its place.