Enforcement is certainly part of it (planners and civil engineers make jokes about the ever-changing number of "E"s involved in planning--engineering, enforceme

Enforcement is certainly part of it (planners and civil engineers make jokes about the ever-changing number of "E"s involved in planning--engineering, enforcement, education, encouragement, entomology, et cetera). From my own experience, enforcement is the number one thing people ask for at public meetings, and the very last thing they are willing to pay for. Enforcement is crazy expensive. Technology, as you point out, more broadly deployable, as well as cheaper and less likely to discriminate. For that reason, I actually kind of like speed / red light cameras. However, they are wildly unpopular to the point of being made illegal in many places. Plus, I think there are legitimate concerns about surveillance aspects of our newly smart cities. With respect to "safer at any given speed" designs, I think you have to consider that, in order for safety to hold, you need to make some unrealistic assumptions about other factors remaining constant. Also, many of those so-called safer designs really do everything possible to eliminate other kinds of roadway users from the mix. An automobile monoculture isn't very robust, and it also assumes the wrong units of analysis. Traffic engineers used to measure mobility in vehicle throughput. Amazingly, if you shift your units of analysis to people, monoculture looks less compelling. And that's even before you consider physical activity, environmental externalities, and a raft of other issues.