Speedbumps help a bit, but many drivers break down just before the bump and then speed to the next one. Better solution is to design the street for slower traffic. Narrow it down, expand the sidewalks and/or add a bike path, Make speeding uncomfortable and the average speeds will go down.
Our state DOT is requiring developers build wider streets (because parked cars), and avoid sidewalks (because maintenance)
Speed bumps do not do much against enormous SUVs and pickup trucks.
Nor do they help against drivers looking down at their phones.
We have regular speed bumps. The cars accelerate back up to 50+mph right after driving over them.