That doesn't track because the real cost to replacing underground infrastructure is not the digging, materials, or labor. We avoid such maintenance as long as possible because shutting down a road is usually very expensive in terms of second-order effects.

Digging up a pipe and replacing it is actually pretty cheap and easy. Disrupting a main thoroughfare is incredibly expensive in terms of lost productivity, transport, shipping.

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refactor_master 4 days ago | parent | next [-]

This just sounds like a different way of saying "one more lane bro, trust me". Usually one doesn't "shut down" a road, but divert lanes, perform construction outside of peak hours (e.g. at night) etc.

Finally, some people may even consider the construction too much of a hassle and use the car less. Empirical studies suggest that "removing" a road does not cause productivity loss overall, since having the road in the first place induces a lot of "non-essential" demand.

	▲	bluGill 4 days ago \| parent [-]
		That arguement is stupid. the world is not only about productivity. If people want to do something just because they enjoy it then they should. If the lack of a way means they do something else that is a loss. The whole point of Cities is all the options, if you want lack of options there are a lot of small towns - and even they have more options than you want to allow. now it need not be by roads - a great transit system should enable moreeobtions. However the point is all the things you can do if you choose not a train or road to nowhere.

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pjc50 4 days ago | parent | prev | next [-]

This whole thread reminds me of the Edinburgh tramworks; despite there having been 19th-century trams on the same street, the modern trams are heavier. So the tram building project turned into a saga of underground "technical debt": sewers had to be rebuilt to take higher weight overhead, which meant digging up everything buried in the road, all the pipes and wires, plus extra bits of archaeology. Hence massive cost overruns.

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PeterStuer 4 days ago | parent | prev | next [-]

It is not cheap nor easy. For many of those pipes, especially yhe waste water ones, there are no AS-BUILDs, and they are unmapped in a very real sense.

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bluGill 4 days ago | parent | prev [-]

there are enough roads in any city as to rebuild a few every year. Pipes don't last as long as pavement in general.

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gnabgib 4 days ago | parent [-]

Pipes have lifetimes of 2-10x roads... where's your data from?

Roads[0]: Asphalt (18 years), Concrete (25 years) - requires good expansion gaps, good substrate, zero roadwork over its lifetime.

Pipes[1]: HPDE (50-100 years), PVC (50-70 years), Reinforced Concrete (75-100 years) Vitrified Clay Pipes (Several centuries), Galvanised Steel (40-70 years)

[0]: https://www.ayresassociates.com/the-long-and-short-of-it-lif...

[1]: https://trenchlesspedia.com/the-lifespan-of-steel-clay-plast...

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amluto 4 days ago | parent [-]

A city could replace pipes preventatively as part of road resurfacing when the pipes are sufficiently old.

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mschuster91 4 days ago | parent [-]

Not that easy. A road resurface, that can be done in a few days worth of work, less if you hire enough machines and staff.

A pipe replacement? Sewer mains at least here in Germany tend to be anywhere from 2 to 8 meters below ground. That's a lot of soil to move. Freshwater mains is below freezing depth, so usually around 1-2 meters below ground. And above that is a ton of other wiring... electricity, phone, fiber, cable tv, gas and district heat/cooling just to name a few, so when you want to replace the sewer mains, it involves a lot of companies, plus the city authorities for coordination, permits, traffic re-routing (a bus route is bad enough - a tram line or a legit full size train line is a nightmare).

Outside of immediate emergency work from a burst pipe, replacement works take years to plan.

	▲	bluGill 4 days ago \| parent [-]
		That it takes years to plan means you have time to work with the road people. We will have to dig this road up anyway don't resurface it. Often they know roads were built sub-modern standard and want to dig it up but it isn't ecconomical. this needs to be done for all roads constantly sometimes the pipes are still good and you resurface, sometimes they will fail in a few years so may as well dig them up since we have to do the road now.