In 2008 I had a 40 mile (each way) commute, and a small SUV. I spent 2 hours on the road each work day. Going slower meant adding more time to that grueling commute. I looked at different routes, but didn't want to add another 30 mins each day in the car. Getting a smaller care meant taking a loss on a 2 year old purchase to downsize (looked a the Prius at the time) and would not have paid itself back in gas for several years.
And with that commute, I felt safer being in a not-small car. 70% of the way was barreling down the highways at 80 mph. Alongside most others far bigger than even what I drove.
So, while size and fuel efficiency can be factors for a future purchase, it's not a behavior most can change...immediately, as any relief for the current situation, or even in the next few months. Gotta get to work, get the kids to school...and like the extra expense, most working families can't afford the extra time to go significantly slower either - which is only a factor if their commute isn't already just stop and go city traffic.
Yes. It took a while for old cars to die out, and for people to accept the new smaller cars as the standard.
As mentioned in an earlier post, the gas shortage in the late 70s/early 80s caused my parents to park their big Chevy station wagon with a 350 c.i. V8 (5,700 cc, perhaps 8 mpg and on the highway) to drive a VW Rabbit with a 1,500 cc engine. At that time, US car makers were in deep doo-doo, because they had no small cars to sell. People bought Japanese and European cars with 4-cyl engines.
When everybody drives smaller cars, you don't feel unsafe. And people will take jobs closer to home, cut back on extra-curricular activities that make them drive all the time.
Europeans don't drive as much as we do. They cannot afford to. People will adapt to whatever they need to do to survive.
What happened in the US was that after each fuel shortage, the oil industry stepped up and drilled, drilled, drilled. Gas got cheap again. No more puny 4-cyl engines. Big V8s got back in vogue.
Rinse and repeat. People never learn. Same with housing bubbles, stock bubbles, what have you. And they complain, and wail, and blame this and that. They blame the oil companies for drilling too much, then not drilling enough. It never changes.