> If it's not working, they why continue?

To the extent that it's already being implemented, who says it isn't working?

> At levels where it does work, you will just disadvantage the less wealthy as the people who can afford it will choose to buy it.

So? Regulation is often a compromise.

> If that's the case, then why not remove commerical trucks altogether since they are disproportionately involved in fatal crashes (11%)?

I think this is pretty obvious: they're a necessary component of our economic apparatus. A shiny new F-150 with an empty bed and truck nuts on the back bumper isn't.

> I don't really like the concept of restricting people for the purpose of reducing their freedoms.

Reducing freedoms isn't the purpose; saving lives is. Should I be allowed to drive as fast as I want wherever I want just because I want to? No; roads are public infrastructure, and we regulate their use for the public good.

> How many people actually buy their type of vehicle due to advertising? In my experience, people know they want a sports car, SUV, or truck.

I would expect this to be a change that takes decades to unfold. But, surely, you aren't claiming that consumers aren't affected by advertising?

> To my knowledge, they still allow larger vehicles, but they just aren't as popular. Is there a specific regulation?

I expect cultural factors are to blame for our obsession with large vehicles (that, as you say, doesn't seem to be shared by the Europeans). So, given that they seem to have achieved a significantly lower road fatality rate per capita than we have, I would suggest looking at their safety regs and synthesizing what we learn there with our own needs in implementing regulation targeted at improving road safety.

> This is highly subjective. A truck is a reasonable and practical size if you live on a farm or participate in specific activities.

This isn't germane to my point. I'm suggesting that we start with "basic car" to establish a baseline for safety, based on certain basic and plausible assumptions about low mass, low bumper and hood height, etc. being safer. From there, we can evaluate the safety of other configurations. This will also give us the chance to test our initial assumptions about what configuration is safest.

> Using this type of language makes it seem like you have bias against larger vehicles.

When they cause thousands of preventable deaths, I certainly do have a bias against them in certain contexts.

> Why not just ban vehicles altogether if that's the basis?

It's a serious question: what is a human life worth?

Is it worth Thanos-snapping every vehicle in existence out of existence right now, all at once? I think the suffering (total logistic collapse) that would result from that action would far outweigh the preventable deaths caused by large vehicles in our current configuration of reality.

So--in practice--we will have to perform some good faith cost-benefit analysis rather than rushing to absurd extremes, won't we? :)

> There can be areas where higher ground clearance is required. Many people still live on dirt roads that can be rough. There are also areas with significant snowfall that this can be useful for. Should we also make handicap vans illegal because they're modified. Even then, what if the geometry change is actually beneficial (rebuilding older cars with modern suspensions, or lowering a truck)? I don't think bans are really going to make a difference and would just be a ham-handed "fix".

I have to wonder if you have any idea how complicated regulation gets because it has to function in the messy real world.

Do you really think I'm suggesting we carve these HN comments into stone tablets and hold them up as law? Or is it your position that if I can't cover every corner case of what would necessarily be a sprawling, thousands-of-pages sort of thing in my HN comments, it's infeasible in practice?

> States do require this. They have safety regulations and many have safety inspections.

To the extent that they actually do have any meaningful restriction of aftermarket mods, enforcement seems to be laughable--much like driver licensing.

> I don't see any data suggesting that specific vehicles [...] will make a significant difference.

Check OP's link at the top of this thread for some, and Google for more. It is not hard to find.

If you're talking about modifications specifically, I don't think the fact that nobody seems to have gone looking yet is a good argument that nobody should go looking. Do you?