OK, what I wrote was incorrect. What I had in mind was that cities spend less than 10% on road infrastructure, but I carelessly didn't specify that. You seem to understand these issues much better than a typical person, and I think you deserve a careful and thorough reply.

> Shoreline WA [2], 22% of the budget goes towards utilities ($82.809m), about 38% goes towards capital projects ($136.065m).

> (...)

> Shoreline School District has a budget of around 160 million [3], which is less than the city spends on utilities + capital projects

First, the Shoreline School District's budget is more like $220M. $168M is just the General Fund, additional $26M go to capital projects, and $35M go to debt service. That's $16k per student, which, by the way, is around 50% more than the private school tuition for my children in Seattle, which does not exactly makes me sympathetic to the narrative of starved school budgets being cut to pay for infra.

Worth noting is that many Shoreline parents pay for private education, but do not pay for private roads or water or sewer. Thus, $220M is underestimate of educational spend, whereas infrastructure spend is not underestimated by looking at the budget.

Second, if the argument is that low density makes the infra spend untenable, you need to compare the spend to the hypothetical spend in the alternate universe where the density is higher. In that universe, we'd still spend on infrastructure, though maybe somewhat less (not a given though: we'd have fewer miles of roads to maintain, but average right of way would become much busier, and work on busy road is typically much more expensive). So let's dive into Shoreline budget to see what spend could look like in more dense world.

The $136.1 capital spend is split as follows:

* $43M is General Capital, and $92M is Road Capital

* The $43M General Capital fund is split into $5M spend on Maintenance Facility, $5M on "Debt Service and Other", and $33M is spent on capital improvements to city parks. I'll assume that all of this spend would remain in denser world (unless denser world means fewer/smaller city parks per capita).

* $92M is spent roughly in half between Pedestrian/Non-Motorized Projects, and Safety Operations (which I assume is mostly motorized infrastructure).

* Half of pedestrian spend is on a pedestrian bridge over I-5, which would still be built if Shoreline was denser (in fact, we might then need more pedestrian bridges). The other half is building new sidewalks. More pedestrians means fewer roads, but more sidewalks required, so it's hard for me to estimate how sidewalk spend which change with increased density, but let's say that increased density means spend on sidewalks could be cut by half, so we'd see something like $15M savings.

* In the Safety Operations (i.e. motorized) spend, large majority is N 145th St improvements. This is the major arterial in Shoreline, and would likely still be part of Shoreline's budget if it was denser. It would probably be shorter then, so let's cut the spend by half. The rest we can also cut in half, for $20M in total savings.

* Worth noting is that road resurfacing spend (which accounts for most of road maintenance) is less than $3M, which is a tiny fraction of the whole budget. Maintaining suburban roads is very cheap.

* Thus, increased densification would result in savings of something like $35M, which is a quarter of capital projects.

* If you do the same exercise for utilities, you'll find that a third of it is surface water spend (storm drains etc), which would probably be cut by half in denser world. Two thirds is wastewater spend, which would be reduced by much less in denser world (as the spend scales much more with volume than with length of the system).

* To sum up, densification would save Shoreline something like $60M, which is a small fraction of educational spend. In fact, much more would be saved if Shoreline School District got its costs under control, to the level of my private school in Seattle.