"Make your family less safe to make strangers more safe" is certainly a hard to sell to approximately 99% of the world.

Would you rather raise your family in:

(0) a place where nobody else can have an SUV whose extra size directly increases the danger to your kids, but you also can't own one to keep your kids slightly safer while you drive them; or

(1) a place where you can have an SUV that keeps your family slightly safer while they're in it, but everyone else can also own one and they make your family less safe whenever they're not in an SUV themselves?

Social rules are, at least at their best, a way to do better than a Nash equilibrium of mutual defection.

Since (0) is impossible, the answer is the one already proposed.

Why do you think (0) is impossible? Do laws not exist where you are? Are you not able to change them?

To make (0) happen you have to force 10s or 100s of millions of people to give up their current vehicle and buy a new one. To some people that sounds feasible, but they're a good bit more authoritarian than the average politician in the US.

It doesn't need to be a Fox news black and white argument about personal freedoms. Impose safety regulations that accounts for the people outside the vehicle, and the overall safety of the streets. You don't need to wipe out current SUVs and trucks overnight.

If they took away gas guzzling V8 engines, they can take away unwieldy oversized light pickups and SUVs.

Most people don’t own SUVs, even in the USA; and even if they did, laws can be local, so it would be your city or whatever rather than everyone everywhere.

But in this case if everyone thinks that way and buys an SUV the world in general is less safe for your family and you're in fact to safer from having a bigger car, if you ever were which seems to be debatable.

False premise

Not to 99% of the world, but to 99% of the people in an egocentric society.

"Make your passengers more safe, by making your community less safe" is also a not an easy sell, but Americans are paying the big bucks to do it.

At some point your family is going to be on the receiving end. We don't have to be so shortsighted.

I completely disagree. Your moral obligation to your own family trumps that of your obligation to society at large. Even if you could argue that it should not be so, it is in practice.

The harm/benefit to society would have to be much larger for even the most altruistic people to give it more weight than the harm/benefit to their own family.

That’s not the case here.

Why is protecting strangers a moral necessity but protecting your own family is not?

I'm not even making that claim here, come on.

If being in traffic is so dangerous to your family then your protective response should be to reduce their exposure to it as much as possible.

People in this thread are jumping straight to their right to increase the overall danger of driving, and put more of that danger outside their personal sphere, before taking any other actions to reduce or mitigate it.

They certainly have that right under the current arrangement. And I'm not saying all evaluations or decisions along these lines are immoral, I can approach this with understanding of real conditions and nuance. But along with that right comes being considered morally culpable or even cowardly for exercising it.

Let's take as a given that heavier cars are more dangerous to be around.

An individual who needs to commute by car has two options:

1) put themselves and their family in greater danger by driving a lighter car.

2) protect themselves and their family but increase total danger to society by driving a heavier car.

I am unconvinced that there is an obvious morally correct answer. What are one's moral obligations to themselves, their families, and their society? How are these prioritized?

You can't just say "don't drive lul". It's literally not an option. We should have better public transportation, but we don't.

For example, it's the only way that some means of disease prevention work.

What means of disease prevention require not protecting your own family?

You have a moral obligation to your own family though. I think that is the point that OP is making.