If that were even possible, car manufacturers would have done something to deal with it decades ago.
They did, up to about 40 years ago they were called quarter windows and were common place
Pure nonsense. The HVAC system in the car has vents to the outside world. How do you suppose it brings fresh air into the car? Those are at least partly open all the time.
Now window glass can crack in a window frame if it gets hot enough, has latent damage, is poorly made, etc. All of which things were true back in the 1940s and 1950s as driving was becoming a mass-public activity. People would come out to a hot car, observe a cracked window and blame it on air pressure. Thus do “old wives tales” and bogus factoids get born and spread.
True. But they were not meant as pressure relief mechanisms.
Modern cars provide cunningly hidden vents. Aerodynamics is a vastly more sorted out affair relative to cars of a few decades ago. Even back in the dark ages, all cars vented the cabin from somewhere near the rear quarters. You could be assured of flow though ventilation through the cabin without any mechanical assistance.
As another Australian, I’m pretty used to the trials of a car that has sat outside all day in 40 C heat in direct sun. A sun shield inside the windscreen at least means you can touch the steering wheel. Forgot to put that up when you part and you will be in a world of pain.
Strategy for handling those sorts of days depends a lot on how good your aircon is. I will usually drive for a short time with the windows down, simply to get the worst of the superheated air out of the cabin. Aircon will be running on recirculate, and once I can feel it doing some good, the windows go up. This usually takes less than a minute. The car will get down to sensible conditions a minute or two later. But cars of yore were terrible. The aircon would wheeze out barely cooled air to the point you wondered why you bothered.
As noted above. A convertible is great. Drop the top and the really hot stuff vanishes. Put it up again, and the tiny cabin would get down to arctic conditions quite swiftly. Helps that the entire aircon system came from a normal sized car, and was cooling a cabin barely a quarter the volume. Heating was similarly overspeced.
Please link that source if you can find it, because I did an experiment of my own today.
When I went to my car this lunchtime, the temperature was only 11C (52F) but in the bright sunshine my car interior felt very warm, maybe even hot. Remembering this thread, I cracked the window a little and got back out of the car. I could see ripples on the ground illustrating warm air coming out of the gap.
IMO it is implausible that had I cracked the window, say, 30 mins before, then that temperature gradient would be maintained, less only 2F or so. There is clearly heat exchange happening.