What is the correct brace position (a.k.a. crash position) for car accidents? The Wikipedia page on brace position focuses on airplane accidents.
https://www.casa.gov.au/standard-page/emergency indicates the brace position is different between cars and airplanes:
The common misconception that leaning forward and placing your head against a stationary object is unsafe probably comes from motor vehicle travel. Sitting upright in an accident is approved behaviour in a motor vehicle, however it is unsuitable for air travel because of the lack of shoulder harnesses and airbags in aircraft.
Edited to answer a comment the question received (I am apparently not allowed to point to which one): one can sometimes see in advance that a car crash may happen, and the car may have passengers. I don't think knowing a crash is coming is hard-to-imagine circumstance: it happened to me, you can look around for Youtube videos or Reddit posts, there are 123,000 head-on collisions per year in the US, and car accidents are much more common than airplane accidents. But it is up to you to decide not to be prepared (Darwinian selection).