Yes, but that’s a do both situation. Many cars are sold which can exceed 150% of the highest speed limit anywhere in the state, and while there are hard problems in designing speed limiters (e.g. urban interstate sections with GPS bounce) it’s pretty much trivial to say that the advanced computer in your new car can refuse to go over 75mph anywhere in the state if California, or reasonable caps in urban cores where there’s no legal place to go >45mph, etc.

The problem here is that changing built infrastructure is expensive and challenging: the most aggressive drivers will fight every change tooth and nail, there will be impassioned arguments about freedom (except for the freedom to be a pedestrian and live, of course) and you’ll hear a million fantasies about how you sometimes need to LARP being an ambulance driver during emergencies in highly improbable situations where driving 90mph to the hospital is a) medically necessary and b) doesn’t result in more injuries. We are seeing improvements but that’s a huge lift, whereas California telling car manufacturers to enable a feature they already have much of the hardware and data for from all of the assist/navigation/self-driving work has the very convenient aspect of not requiring thousands of CalTrans and local projects to be planned, survive approval, and be built to start saving lives.

What I would like is to pair this with mandatory improvements as part of routine maintenance: every urban road resurfacing, ADA upgrade, etc. project could include safety improvements so those don’t require expensive new projects which might involve ripping up roads worked on just a few years earlier.

One example I like are continuous sidewalks / raised crosswalks where cars have to go up an incline to pass through a pedestrian space or bulbing out corners so drivers have to slow down. You can’t easily deploy those everywhere but there are a ton of areas where it’d be easy and important around schools, parks, etc. and if you could flip it so the planners would have to get an exception approved _not_ to use a safe design, cities could roll that into normal maintenance and be much safer a decade later.