my one pet peeve around that is that most californians don't respect the rule that any intersection of two city streets is a crosswalk, whether marked as such or not, and pedestrians crossing at a corner have the right of way. as soon as they start walking, cars must stop for them, even on larger streets (most drivers don't know/rememeber this and zoom dangerously close by).
Slower roads (max 20MPH/30KMPH) should be bicycle and pedestrian-first.
all roads, but even residential streets, in car-centric cities like LA seem to be built wide enough to accommodate 747's with ease.
my proposal: rather than 12-15 foot widths, make urban residential street lanes 9 feet wide (cars are typically 6-7 feet wide, delivery trucks, 8 feet wide). replace parking lanes with slightly grade-separated (3-4 inches) bike lanes, leaving existing walkways for pedestrians only.
and make sure these narrow lanes have shoulder lane markings.
In one street of my city the parking was replaced with two way bicycle lanes, and there are plastic bollards to separate it from the road (which is probably around 9 feet now as you suggest). Compared to a grade separation that isn’t going to do much if you go over it, if you hit a bollard it’s going to leave a nice permanent mark on your car, so you are going to drive more carefully.
The only issue I’ve seen with this is if vehicles need to deliver to the shops and bars on this street, they have to park in the cycle lane (there is no rear access or parking).
Slower roads (max 20MPH/30KMPH) should be bicycle and pedestrian-first. Cars there should be "guests" catering to the slower non-motorized traffic.
This way we have the best of both worlds: nice & livable urban roads and faster driving in connecting roads.