So make the lanes narrower and add speed bumps to slow people down, and also make a passing lane for every speed bump and expect assholes not to use it? Almost as clueless a suggestion as the generic "just redesign every street and intersection in every city to make driving faster impossible!"

Barriers have their place and I don't mind having a narrowing area and speed bumps in front of a school or in a parking lot or whatever. But in a lot of places a camera is a simpler, cheaper, easier, better solution.

And a fire truck or Ambulance is quite capable of going 20-30 above a speed limit in an emergency most times of day and days of the week. I think as a society we take that small increased risk, balancing it with sirens and special driver training, so that people can have help arrive as fast as possible.