I'm going to sound like Jeremy Clarkson here, but I detest the damn things. I counted them on the way to work today and I go over 28 of the bloody things on my way to and from work. When the Sydenham traffic calming meaasures are completed this will swell to 40 a day on my way to and from work. It is not uncommon for me to go over 70 or 80 a day.
The contracters who are responsible for the Inverary scheme appear to have done all their measurements by guesswork, we have the biggest speed bump in the world at Sydenham train station, approximately 20 feet long, at the bottom end of Inverary they have made a rectangular speed dump, a six inch high 90 degree kerb on the approach side and a 8 inch drop at the far end. If you go too slow your car just stops.
There are alternatives, I was reading about retractable speed bumps, that lower when you are travelling at a suitable speed. There are also traffic calming measures on Island street that make you zig zag through a set path. These work well and give you an added challenge of seeing how fast you can make it through the maze.
Incidentally the Ulster Clinic on the Malone Rd have a much better class of speed bump...speed retarders they are called.