Healthy? Didn't someone quote figures before on this here which showed that levels of pollution are higher when cars at being driven at 20 mph rather than 30?
I agree with Chris - the 20 limit (doubtless unintentionally) causes much more visible anti-social behaviour in drivers.
There's a point to be made about collision outcomes. Cyclists hit by drivers coming too close are one thing, but for pedestrians whose survival rates are changed, why are they being hit by cars, anyway? Isn't there some education needed on safe road crossing?