Riven, good points, to add to them, I'll say the following:
I'm aghast at the glib nature and hand waving on speeding in built-up areas on this thread. Perhaps those of you who don't yet 'get it' need to see it explained another way...
Hit anyone above 25mph and you will, more likely than not, kill them...
It takes 75ft to stop at 30 mph.
It takes 105ft to stop at 40mph.
Therefore if you are driving at 40mph in a 30 zone, a child runs out 75ft ahead of you,
You slam on the brakes...
You will STILL hit them at 29mph.... probably killing them instantly.
Who in their right mind would, at 30mph in a 30 zone, merely lift their foot off the accelerator pedal when a child runs in front of them? This realistically is what only being able to reduce your to 29mph effectively equates to.
This is a parenting site, for all of you that have said you'll try to slow down, imagine what excuse you'll tell the parent of the child you may kill? Or what excuse you would find acceptable if it were your DC killed?
Please DON'T speed in 30 mph zones.