'Traffic calming measures' is one of those misnomers that has become common in the English language now. You know the things - bollards, speed bumps, narrow sections of road, stripes - all manner of stuff to divert your attention away from the matter at hand -- driving. As far as I can tell, these things just serve to aggravate the average driver. I can tell you it works for me.
If I'm driving down a road with a 20mph speed limit and I see speed bumps, I'd like to believe that I'd be able to drive over them at 20mph. In most cases of course, even the biggest Chelsea tractor couldn't make it over a speed bump at 20mph without rearranging the litter of kids in the back and causing untold damage to the suspension. Surely it can't be that difficult to make a speed bump that you can navigate at the intended speed limit?
Then there's road-narrowing and bollards - both items which typically take me by surprise and cause me to brake because the illusion is that the road is becoming too narrow to drive down. The person following me brakes too - if he's seen me - and suddenly you have a street full of erratic slow-down-speed-up driving. It's all so very unnecessary.
I pity the poor soul who has to ride in an ambulance down one of these hump-ridden streets when they're in cardiac arrest.
I would argue that traffic calming measures typically make those streets more dangerous than they were before. When the neighbourhood kids run out into the street in front of us now, are we going to be concentrating enough to see them, or worrying about the next Everest-sized speed bump?