Originally Posted by ThePhun1
It'll be interesting to see what becomes of suburbs in the coming decades as oil, if not drying up, becomes more expensive along with gas and as the infrastructure in suburbs becomes older. I think the Rust Belt will take the hardest hit but I could see some Sun Belt areas, such as perhaps Phoenix (especially if water stays an issue) start to resemble San Bernardino in a few places. San Bernadino is the prime example of what a decaying ruin a suburb can become.
Las Vegas already flirted with this disaster about a decade ago with entire neighborhoods resembling ghost towns.
Some suburbs might manage, they could become rather different places in the future.
For example the typical auto-oriented suburb might have transit mode share of 5%, and the combination of low mode share and low density means that transit sucks. But imagine if density stayed the same and mode share went from 5% to 50% or even higher! We have a hard time imagining suburbs with good transit, but that's partly because we have a hard time imagining them having such high mode share, because really, there's no reason for it right now that gas is cheap and driving is faster. Even highly urban neighbourhoods often have similar amounts driving as taking transit today.
As for mixing of uses, right now many suburbs are very bad at it, but perhaps the local strip mall will be converted to light industry, and residential space will be used for small businesses and cottage industries. In order to accommodate a more varied demographic (age, income...) some houses might get converted to duplexes, boarding houses or whatnot. That would likely lead to an increase in density as well. Space dedicated to car storage could get put to other uses (even if gas prices don't change but driverless cars come into play) whether that's garages converted to accessory dwellings, workshops or small shops, or parking lots getting converted to squares, parks, or getting built up.
Fences blocking access to roads, strip malls, or between subdivisions will get torn down. Even culs-de-sacs could get connected, you don't need to connect them with a full-sized road that will require houses to get torn down, just a small pathway for pedestrians and cyclists cutting through what are currently side-yards should do fine.
If high gas prices means there is tons of excess road space, then you now have some nice ROWs that can be used for other forms of transportation. Transit will speed up if it can get dedicated ROWs on the cheap, and if the need for transit lights is reduced and most can get eliminated. Isn't ROW acquisition the biggest cost by a good margin for BRT and LRT (and freight and commuter rail)? Traffic lights are mostly needed when you have dozens of cars per minute trying to get through an intersection. Bikes and pedestrians are much more nimble and don't need traffic lights to move around each other, and transit vehicles would still only come once every couple minutes so pedestrians and bicyclists can just wait for them to pass.
Even with the new transit ROWs, there will likely still be a lot of excess road space. Arterials could be narrowed from 6 lanes to 2 lanes with multi-use paths. Side streets could go from 30-40 ft curb to curb to maybe 15. Driveways could be eliminated. All that excess asphalt could be converted to open space or built up, which would also reduce maintenance costs and increase density. Reduced wear and tear from cars and trucks would reduce maintenance costs as well.