I don’t think any road that has kids playing shouldn’t have a fast speed limit. And any road with faster traffic should have no street parking at all, better visibility from the sidewalk, and probably some separation (deeper curbs?). This is regardless of whether AI or people are driving.
Slower speeds work for sure, but getting a robo taxi to adhere to those slower speeds is much more realistic than getting a human driver to do the same.
Road design sends signals to drivers: wide lanes and other design choices make a road less cognitively stressful, and so you speed up. It feels like you should be able to move a bit faster, and so you do. If the posted speed limit doesn't feel right, drivers will ignore it.
The answer is to take that into account with traffic calming measures[0] that alter the street design and make it more stressful for drivers. Narrower lanes, big trees overhanging the street, small traffic circles, pinchpoints, and other measures making driving fast very uncomfortable. You feel like you need to pay more attention, and drivers naturally slow down as a result.
The Dutch have figured this out, there are plenty of things you can do to make roads better and safer for pedestrians, we just don't do that here in the USA. It is just that, if drivers could be controlled, you could focus on more pedestrian/bike safety and expect cars not to go too fast (assuming all cars were self driving, which won't happen for a long time in the states at least).
Slower speeds work for sure, but getting a robo taxi to adhere to those slower speeds is much more realistic than getting a human driver to do the same.