Munich built a 4.3-kilometer tunnel in 1972. That tunnel turned twelve disconnected suburban rail lines into a unified transit system that today carries 840,000 journeys per workday. The tunnel cost $2.8 billion in today's money. The suburban lines it connected were built in the nineteenth century. For less than five kilometers of new construction, Munich got a hundred kilometers of metro-quality service.
Benedict Springbett's essay on through running is about trains, but the principle it describes is about something more general: the disproportionate value of small connections between large existing systems. The Victorian suburbs of Munich already had stations, tracks, trains, and passengers. What they didn't have was a link through the city center. Add the link, and the whole system transforms. Remove it, and you have twelve separate rail lines going nowhere in particular.
The contrast with London is instructive. London had even more suburban rail than Munich — an enormous network built by competing private companies in the nineteenth century. But the competing companies didn't want to share infrastructure. Each built its own terminus on the edge of the city center. The result: a hubless wheel whose spokes never connected. London's first attempt at through running opened in 1866 and closed in 1916, outcompeted by trams. The next serious attempt, the Elizabeth Line, wasn't approved until 2008 and didn't open until 2022. A century and a half of knowing what to do, and not doing it.
Why? Springbett doesn't spell it out, but the Hughes reading on the Great Downzoning suggests an answer: interests, not ideas. Through running in London would have required private railway companies to cooperate, governments to fund tunnels, and neighborhoods to accept construction. Everyone agreed it would be beneficial. Nobody had sufficient incentive to make it happen. The idea traveled fast. The interests didn't align for a hundred and fifty years.
What strikes me most is the ratio. Munich's tunnel was 4.3 kilometers. The network it created is over a hundred kilometers. That's a leverage ratio of roughly 25:1. The Elizabeth Line's tunnel is 21 kilometers and created a 117-kilometer railway — about 6:1, still remarkable but a fraction of Munich's efficiency. The difference: Munich planned the tunnel as part of a unified system from the start. London bolted it onto a fragmented legacy network decades later.
Springbett estimates that 90 percent of London's S-Bahn network already exists. For Manchester, it's 95 percent. Boston needs a single mile of tunnel. The infrastructure is there. It's been there for 150 years. The missing piece is always small relative to the whole — a tunnel, a junction, an interchange. But the missing piece is everything, because without it, the system is just a collection of parts.
There's a pattern here that I keep seeing: the value of a system is not proportional to the size of its components but to the quality of connections between them. A hundred kilometers of disconnected track is less useful than five kilometers of tunnel connecting them. The expensive-looking solution — build a whole new metro — is often less effective than the cheap-looking one — connect what's already there. But the cheap-looking solution requires something harder than money: coordination, foresight, and the willingness to invest in connective tissue rather than new organs.
The essay ends with a quiet rebuke to the technology industry's reflex toward novelty: "It is tempting to think that the most important ways to improve transport involve new technology: self-driving cars, flying taxis, or even e-scooters. But often, the best investments involve getting the most out of existing technology." The most boring solution — connecting Victorian rail lines with a tunnel — turns out to be the most transformative. Not because tunnels are exciting, but because they complete a circuit that's been waiting to be closed.