A lot of the other infrastructure involved in sprawl is not sustainable, since it was funded by federal dollars but its upkeep/replacement will not, especially water and sewer mains/service
I suppose it depends on what we're defining as infrastructure.
* Roads can be built to last 15 years before needing additional work (routine maintenance extends this to 20 years), same with sidewalks.
* New sewer and water pipes will last ~50 years.
* Copper electrical cabling will last at least 100 years, but lets be conservative and assume only a 50 year service life before you have to pull new wire through underground conduit/concrete channels. Let's also assume more solar goes on suburban roofs (and batteries in garages) as the cost continues to decline, taking load off of the traditional electrical distribution network
* Estimated service life of fiber optic cabling is 25 years (fiber to the home)
* The suburbs will never be dense enough to satiate transit demands using busses or light rail exclusively; it's EVs most of the way (sustainably powered by either distributed or utility generated renewables). I am a huge proponent of electric busses and dedicated lanes for them in high density areas whenever possible. Faster and cheaper to deploy than light rail, and more versatile for changing needs.
Nothing above seems unsustainable to me, but I also agree the suburbs should not be subsidized.
Why would anyone think the infrastructure business with extremely high marginal costs, low reproducibility (each situation is different), high labor costs, high legal costs is comparable to technology (presumably electronics), which have low marginal costs, and more one size fits all solutions.
Yeah, I don't see many obvious places to trim. Living spread out like as in the suburbs but with city-like infrastructure seems like just a fundamentally expensive way to live. Good for stimulus spending, except that these aren't really assets that boost output to cover the interest, so then there's the maintenance hangover.
