Previously what was used was a male crash test dummy but sized down. The word "dummy" makes it easy to overlook, but they're pretty technologically impressive bits of kit. They take into account the density of different tissues and their relative distribution in the body, and there are strategically placed sensors to measure the force distribution at different levels. It doesn't encompass all women's body types, in much the same way that the male dummy doesn't encompass all men's body types.

Lots of little differences between male and female bodies cumulatively result in the vehicle collision injury stats that others have quoted elsewhere in this thread. Things like the centre of mass being different, the outline of the pelvis/hips (which also affects the way one sits), women having a greater body fat percentage, that body fat being distributed differently to men's, women have less muscle. Then there's boobs, which aren't just something that can hinder seatbelt placement, but they can also be heavy, and bouncy, which means that the forces involved in a collision can be multiple times more than their weight, which contributes to whiplash and other injuries. On top of this, there's probably a bunch of other factors that we aren't aware of yet, but a more comprehensive testing process could help us to understand what differences between male and female bodies actually matter when it comes to vehicle safety. For example, on average, women tend to have longer hair than men, but I don't expect that would particularly impact injury rate in a vehicle collision. Women having larger breasts than men however, is most certainly a factor that contributed to the stats for women's injury rates being so much higher than men's.

On top of all this, before a dedicated female crash test dummy was designed, the downsized male dummy they were using was laughably small — the male one was designed to be the size of the average man at the time, whereas the downsized male one was so small that it only represented the smallest 5% of women at the time. That just seems absurd to me, but it's what you get when 50% of the population are treated as an afterthought, I suppose.

On the question of does an anatomically correct dummy help, it's a complex question because it takes time for the developments in car safety to actually make it out to the consumer, and even now we have a better crash test dummy for women, some manufacturers have been sluggish in implementing it into their testing — though now at least it's possible to apply pressure and say "hey, why are you not using this in your testing when women are at much higher risk when in one of your cars". Previously, manufacturers who were challenged on this could just shrug and blame the lack of an anatomically correct female crash test dummy, and development of one of those took a lot of time and research expertise, so wasn't something that could be done trivially. Now the resource exists and the industry has less of an excuse.

Crash test dummies test the impact of vehicle accidents on human bodies. While more men than women are injured in vehicle accidents, they are more frequently involved in them in the first place. Women are 17% more likely than men to die in the event of a car crash, based on university studies in the US, and 73% more likely to sustain serious injuries in a front-end collision (Invisible Women, p186). In the world of crash test dummies, ‘human body’ has really meant ‘male body’; the first anatomically correct female crash test dummy was only created in 2022.

https://www.theactuary.com/2023/02/02/when-human-isnt-female

Before intervention

17% more dead women than men

73% more injured women than men

When women are in fewer crashes overall

First thing that springs to mind is the chest strap on a seatbelt interacting with boobs

Do those also account for pregnant people (masc, fem and enby)?

"An anatomically correct female crash test dummy is a test device designed to more accurately represent the body shape and dimensions of women, particularly in areas like the pelvis and upper chest, which are more vulnerable in car crashes. These dummies, unlike the older scaled-down male dummies, incorporate features like a female-shaped pelvis, breasts, and a lower center of gravity to better assess how different car safety features affect female occupants."

-Google AI Overview