Why is it when there is any mention of 20mph limits, traffic reduction safer roads and improvements to health and air quality this is met with opposition?
The answer I believe is Cognitive Dissonance. This is a psychological theory which suggests that people have a strong inner desire to hold all their beliefs in harmony, and that we avoid any disharmony (or dissonance) in our own minds.
If we are presented with information which conflicts with the beliefs we already hold, one way to mend the dissonance, and to restore harmony within ourselves, is to discredit or disbelieve the new information.
I have seen this many times while debating 20mph speed limits. People will try to argue that: 20mph speed limits are pointless, will make no difference, will even be counter productive to safety health and air-quality, or that the people who want safer roads and cleaner air are meddling 'do-gooders' with too much time on their hands and should 'get a life'. But at the same time they will go out of their way to overlook, discredit or try to disprove any counter argument, data, or facts that conflict with their original belief. This is as to maintain 'cognitive harmony'.
"And that Mr Crawford is a complete load of Psycho-babble..."
(Which as a response proves my point).
So while people appear to be trying to debate issues, what they are actually doing for much of the time is seeking support for the beliefs they already hold and trying to discredit anything which goes against it, thus preserving their cognitive harmony.
People like their cars, I get that, I like mine too. They like the convenience of them, they like the freedom and care-free travel which they can provide. They also want to drive as fast as they like, as much as they like and wherever they like and they feel they have every right to do so. They also pay a lot of money for their cars and pay a lot in taxes to use them. Many drivers also see their cars as a status of their success or a symbol of their importance in the world or even an extension of their personality. So if anyone starts staying that they should drive less or drive more slowly, this is going to cause cognitive dissonance. Which is why no matter how well reasonable any proposal to reduce traffic speed and volume is, it will be met with opposition.
When people hold a strong belief and they are later presented with evidence that goes against that belief, the new evidence cannot be accepted as it would create a feeling that is extremely uncomfortable. It is so important to protect that belief, they will ignore or even deny anything that doesn't fit in with that belief.
So what we need is a change in attitude, or if necessary, a change in belief. Particularly in the way we see cars and transport. We need a change in attitude towards how we perceive other people on the roads, towards the environment, towards the air we breathe, towards health, towards safety and ultimately towards how we most effectively and efficiently use our cars and see them for what they really are.