If you put speed bumps on the road then the cars will veer around them into the shoulder trying to avoid having to slow down. Some will soon learn you can go 35 to 40 over them and not even be able to feel they are there. Trucks with unsecured loads of trash and construction equipment will send nails and screws and other tire-puncturing things into the street whenever they go over them. And the bumps will get in the way for the cyclists, too. In my experience (I live on a street with speed bumps), speed bumps are a poor solution.