I'm confused: what didn't work in Seattle/SF/Portland?
Enforcement didn't work because people won't follow the law anyway or engineering didn't work because people tried to drive through the obstacles or approach them with the same speed and smashed/smooshed more?
SF tried a multi-front approach called "Vision Zero". I think initially deaths went down for a couple years but then ticked back up. No, people aren't (usually) driving through obstacles.
Enforcement didn't work because people won't follow the law anyway or engineering didn't work because people tried to drive through the obstacles or approach them with the same speed and smashed/smooshed more?