Why Doesn't Boston Have Red Light Cameras?

According to a Liberty Mututal article I read recently, 550 cities and towns in 25 states have already adopted red light cameras at intersections. They have proven to cut driver collisions (30% according to a study by the Texas Institute for Public Safety) and help keep the roads safer for bikers and pedestrians.

According to 2011 study by the Insurance Institute for Highway Safety, the cities with cameras reduced their total number of red light crashes by 24 percent. 

In light of shrinking city budgets, it seems like a good way to do the work that police don't have the man power to do anymore. It also sends a strong message to residents that your safety matters.