When car_a is trailing car_b at 60ish MPH and car_b suddenly brakes, car_a traverses 150 feet or so before its driver notices danger and stamps on the brakes, and an additional 150 feet are traversed after the brakes are engaged. (It's more complicated than that and it's more complicated than that, too. If I'm oversimplifying too much at this phase please let me know.) So obviously the stopping power of the vehicle is important. Now, a huge amount of R&D has been done on automobile braking systems. Not only are modern braking systems automatic supersonic hypnotic funky fresh, modern cars can extract modern energy out of them, too. But... well, I'm having a lot of trouble finding credible statistics, but it looks like a large fraction of the victims of fatal car accidents are in vehicles that get rear-ended at high speeds.⁰ Not only do they cause a lot of immediate deaths, rear-ending accidents also cause a lot of damage to both vehicles and nervous systems (whip-lash), and it's hard to calculate how that compounds over the years, but you know it's a really huge amount of lost QALYs and moneys. What I don't understand is, it naively seems to me that there are many different ways you can get a tailing vehicle to stop faster, ways that don't involve completely hopeless public education drives or expensive 5% improvements on disc brakes. Like, having a special system specifically for applying high friction directly to the road surface in emergencies, either mechanically or via electromagnetism. Or an air brake^0.08 or two. Combine those with existing automatic electronic sensor brake activator thingies and you can stop the vehicle almost immediately.¹ Wham bam, way less crushed organs and needless suffering. But I never hear anyone talking about this. Is it because modern cars just don't crash into cars in front of them anymore? If so, would it be too expensive to equip older cars with a simple brake-pressure-remotely-activated dedicated stopping mechanism?¹⁴ E.g. a government or non-profit program that equipped them free-of-charge on the cars of inexperienced or risk-prone drivers. Or something? I can think of a lot of engineering point and counterpoint that would make it more or less difficult but it still seems feasible, life-saving, and money-saving. What am I missing? What hard steps did I trivialize? I am more interested in automobile engineering steps I naively trivialized, but social engineering steps that I ignored might be more important somehow... what gives?

^{(This has many connections to both instrumental and epistemic rationality} _{but unfortunately it would be too psychologically difficult for me to point them out.} ^{I do not think a meta discussion about this would be profitable}_{, but I may be wrong.)}

⁰ I saw somewhere that most fatal accidents involve only a single car. That agrees with my experience but I remain somewhat skeptical.

^0.08 More specifically, some reasonable hybrid of air brake and uber-efficient-mini-parachute. I don't know how negligible the stopping power of air brakes is at freeway speeds.

¹ Stopping too fast does indeed hurt the driver but it's rather asymmetric, you can deploy various safety mechanisms in advance unlike the case where you're crashing into an unsuspecting Honda with your Chevy.

¹⁴ I don't see why making such add-on systems at least half-automatic should be hard either, it's like 2 cheap cameras and a rudimentary but information-efficient AI... or maybe I just completely underestimate the complexity of those systems.