Just looking out my front door (suburban DC)… the road is posted 35mm but you can “safely” go 50+ because the lanes are wide and relatively straight. But, there are uncontrolled/no-signal entrances to neighborhoods every 1/4 mile or so, so speeds really should be <30mph (IMO). There are very few signaled pedestrians crossings, so if you need to cross, it’s a game of frogged, or walk a mile out of your way to the nearest full intersection. The bike lanes on the road are just painted on, no protection for cars. And on and on. None of this requires more space - just DOT employees who can think beyond getting around in a car.
We could easily slow the road by narrowing the lane. We could easily add signalled ped crossings. We could easily make the sidewalks continuous (same grade through intersections instead of road level - the benefit is cars enter “pedestrian space” when crossing instead of the other way around). We could add floppy bollards (not sure what they’re called) to give more separation between cars and bicycles (won’t stop a really bad driver, but will at least stop cars from using the bike lane as yet another car lane).