In Walt Disney's opinion, you could bury the streets, too. Utility corridors (or "utilidors" — https://en.wikipedia.org/wiki/Disney_utilidor_system) are essentially the road equivalent to a subway systems' rails.
There are some existing pedestrian-only underground city corridor systems, such as https://en.wikipedia.org/wiki/PATH_(Toronto); and there are many vehicle-only road tunnel networks underlaying modern "walkable" cities, mostly in Europe. There are even a few cities that already have both (e.g. Dubai), although they just have separate pedestrian and road-tunnel networks that don't connect.
Disney's vision was to marry the two—to treat them as an interconnected network, as we do today with the road network (which spans everything from walking trails in parks, to residential streets with bike lanes, to grade-separated freeways.)
We haven't done it yet, but there's not much stopping a city planner (especially of a new city, e.g. a charter city) from doing it. We really could have a "roadless" and even "streetless" surface, with only buildings and parks visible.
(IMHO, it'd be very good to try this first in an area that gets really hot, like Arizona, since you'd get the dual benefits of 1. keeping people cool on their way between air-conditioned buildings by relying on the natural thermal buffering of the earth; and 2. greatly decreasing surface albedo compared to cities that have tons of blacktop. Maybe make a city ordnance that all buildings—and especially rooves—have to be light colors, to boost that effect.)
Do those tunnels actually go to individual homes? I can understand subterranean arterials but would each house actually have direct access to a tunnel? How does that work? Is my garage underground? Does everyone have a basement with an "outside" door?
How does a fire truck or ambulance get to my house? Do deliveries get dropped off underground?
Not the whole garage (unless that looks better, or is more space-efficient), but it’d probably exit underground, yeah.
I would expect that under this model, due to the costs of digging and the economies-of-scale of shared digging, most housing developments (even single-family housing developments) would lean away from SFH garages, and toward neighbourhood autopools (like the parking floors of condo buildings, but not attached to any one building), where you could walk (underground) from your house to the autopool, then drive (underground) from the autopool onto the auto-tunnel.
> Would each house actually have direct access to a tunnel?
Probably not. Big condo buildings would. Townhouse developments might, since you could just build one tunnel “across” a stretch of homes with regularized entrances. (Though these might necessarily be clumsy, tight stairways.)
I would imagine, in suburban areas where you’ve mostly got individually-developed single-family housing†, you’d likely have above-ground pedestrian walkways connecting a neighbourhood’s worth of houses to a ground-level pedestrian utilidor access point. Like a street-corner subway entrance, but without the subway. (I mean, the subway would be there, but you’d get to it with more walking through the utilidor.)
† Not that “suburban” makes much sense to talk about in this context, for various reasons, but it might be relevant to retrofitting projects.
But, presumably, the utilidor would be “shared public/private infrastructure” just like the road system is—so if you wanted a direct access from your house to the pedestrian utilidor, or from your garage to the auto-tunnel, it’d just be a matter of spending the money to get it dug out yourself, rather than about getting the city to do it for you. (Presumably you’d have to hire city-certified engineers to do the work, but that’s true of any digging you do in city limits today.) And that means that you could probably find developments with their own private utilidor access as an amenity.
