The following infrastructure is merely an indicative selection of requirements should only a small portion of climatic and environmental crises eventuate.
Garbage treatment. The electronics and to a lesser extent the chemical/plastics industries are land pollution timebombs that will toxify watertables unless intercepted, a complete recycling process could ultimately pay for itself but would require large up-front investment, probably public, in mining trace elements, flotation separation plants etc. It requires public money because any capture of pollutants has to be global, uniform, not only from cashed up "marketplace" environments. Private enterprise reclamation would, and does, focus only on businesses and other large scale electronics users where it can implement focused economies of scale but there are enough computers and electronics in general public possession to poison water tables when they fully enter the waste stream; however the public effort should be substantially funded by the manufacturers and retailers who were the major beneficiaries of this industry.
Water Supply and Sewerage - Increased population will critically stress fresh water supplies, and this will be global, with few exceptions, in the first instance this will require governments to protect, and possibly buy, land abutting catchment areas, this will need also private industry activity in allowing and providing rooftop catchment but ultimately will probably require desalination plants (so far only affordable in oil rich gulf states) and greater conservation of wastewater. This needs some separation of chemical from organic sewerage flows, then the sewerage will need be treated and reclaimed, by filtration, and the solids used in either worm-farming or methane production and liquids as greywater. Cities will need alternate drainage, possibly into some storage and usage system because, in the event of extreme flood/drought gyrations, water stress will at other times be critical. These of course are major public works projects and will be impossible unless the haemorrhage of funds into the car culture can be stemmed.
Flood, heatwave/fire and storm/cyclone (global warming) preparation. Even beyond those island and delta regions that will flood and whose inhabitants will need resettling, urban sewerage and stormwater systems the world over will back up and flood with seawater rise and this could bring epidemics, particularly cholera. Some shorefront cities will need extensive seawall development for higher tides. Climatic disruption will bring storms, of wind, water, snow and fire, probably requiring the establishment of emergency services at the scale of a standing army, another defence budget! (more 1)
Energy Conservation and Ordinary infrastructure maintenance & replacement.- Much of the infrastructure in the western world was put in place in the 19th and early 20th centuries and is degrading as money is ploughed into highways and "doughnut effect" ring development. If major energy crises are to be avoided during the oil crisis a rolling refit of industry and dwellings to improve energy efficiency through insulation, cogeneration, climatic design etc. will be mandatory, with major public sector investment, this includes an upgrade of all gas distribution systems, a refit of pipes, seals, valves etc. the same is true of the water distribution.
All these are included in car's costs because they a major opportunity cost, they are the things that public investment in the car system currently prevents from even receiving serious consideration, even in those countries where the money and construction/technological capacity would be available, such as Japan, the car mental hegemony siphons it all off into building useless highways and bridges. In a car ban context they would attract more attention.