NTSB investigates hundreds of "major" highway accidents per year. Typically accidents with multiple fatalities and at least one of the vehicles being operated for hire. For example NTSB investigated the Schoharie limousine crash where 20 people died.

Graduated drivers license laws for young drivers, age-21 drinking laws, smart airbag technology, rear high-mounted brake lights, commercial drivers licenses, and improved school bus construction standards all came about at least partially due to NTSB recommendations.

This is a good discussion point: we could do this with car crashes, but I would guess that most causal factors can be summed up as "driver inattention".

How would you solve that? The FAA can issue all sorts of regulations requiring rest breaks, fatigue detection, etc. -- be sure you're ready for that level of intervention before you ask for this level of investigation.

Car crashes are actually the perfect example, because car fatalities aren't just a function of engineering a safe and sturdy car, and human inattention both can't be eliminated, but also isn't independent of design.

For instance, how many people ride in the car? What is the average car trip length? Why and when are people driving? Speed profiles, line of site in both car and environment. Does traffic all flow one way, can a car ever land in incoming traffic if it loses control, are traffic barriers designed to bring an out of control car safely to rest with good line of sight to the accident? Are features keeping drivers alert or distracting them?

The difference between lots of fender benders with a bit of panel beating and constant fatalities can come down to multiple causes, many outside of engineering a safe car.

"be sure you're ready for that level of intervention before you ask for this level of investigation."

There's no good reason not to, for example, have every car use a breathalyzer to start the engine -- those driving drunk on occasion would protect themselves from DUIs, lives would be saved, etc. Or to implement other, similar deep regulations. But the ideology around cars ("freedom"), vs. planes ("safety"), is too different to allow for such levels of intervention.

The good reason not to install a breathalyzer in every car is that I don't drive drunk and would vote against any politician foolish enough to suggest something so intrusive.

You don't drive drunk, but other people do. breathalysers are only put in AFTER an offense. To eliminate the "first generation" drunk driving accidents would require preemptive installation of breathalysers on every car.

The way they are implemented now would be similar to only installing seatbelts in cars where the driver has already been in an accident. Similar sentiment was around when seatbelt laws were put in place, "I'm a good driver." but the seatbelt protects you from yourself crashing as well as when someone else crashes into you!

In the same way, breathalysers (ignition interlocks) for everyone wouldn't be "for you" as much as for everyone to prevent them from drinking and crashing into you.

I hadn't thought about widespread ignition interlocks, and obviously there would be a lot of public pushback, and it would be quite intrusive, but I could see it helping reduce traffic fatalities dramatically.

I don't care how much it would reduce traffic fatalities. I am absolutely opposed to this level of nanny state overreach. And I trust that enough other Americans agree with me to prevent this kind of nonsense from making it into law.

What I would support is a further reduction in the allowed BAC, and stricter enforcement of traffic laws in general.

If you don't drive drunk, what do you lose from starting the engine via breathalyzer, rather than via key turn? Why is one more intrusive than the other? Most governments already require you to carry insurance, have a license/training to drive, wear seat belts -- in what way is this different?

Cars could never be invented in today's legal environment.

About 80% to 90% of reports would state it was operator error on the part of one or more of the drivers involved. Cars are pretty safe when people aren't drooling, lead-footed maniacs.

Huh? 80-90% More like 99.x%. Modern cars are extremely reliable, and even if they do fail (usually due to poor maintenance), that rarely causes a crash, since a disabled car can easily pull over to the side of the road, unlike aircraft.

Almost all crashes are ultimately caused by driver error. Doing FAA/NTSB-style investigation on them would be pointless, because that's exactly what they'd find: people were driving recklessly, inattentively, etc. And there's nothing that can be done about that, because we as a society absolutely refuse to have serious driver training and any standards for driver conduct. We can't even agree on whether the left lane is for passing or not! Try driving in Germany sometime and you'll find that what we accept from drivers here in the US is really quite awful.

To be fair, probably 80-90% of NTSB aviation investigations final reports contain the words “pilot error”.

The term "pilot error" is outdated, and suggests blame. "Human performance factors" is usual way to describe such mishaps.