if a restriction is introduced which then needs another 10 restrictions to make it work I would say you are venturing into a regime of excessive control.
If such great lengths are required to stop inappropriate streets being overwhelmed by cut-through traffic, I'd ask what the fundamental problem is - and my answer would be that it's the traffic itself, not the attempts to calm it.
I get the basic principle of what you are saying - if a system needs ever more additions to make its central aim work, it's an indication that it's not a good system ("there was an old woman who swallowed a fly").
But from my viewpoint it's an indication that our system of giving motor vehicles assumed priority in urban residential areas is not a good one. Just look at the massive amount of infrastructure that's required to allow us to co-exist with motor traffic. All the road markings, rules of the road, testing, signage, traffic lights, complicated parking zones, emergency response systems, enforcement agencies etc. As Brixton Hatter said, roads haven't always been the domain of vehicles travelling at such a speed that they can kill you if you step out in front of them, and there's no reason they should remain so.
Does a laissez-faire approach where we just trust drivers to take into account the effects of their journeys on others work? No it doesn't. People ignore speed limits when they can get away with it, and they will take short cuts through small residential streets if it makes their journey a bit faster. This is the problem that these measures are trying to solve. To fight against this tide at a local level, it's currently necessary to implement complicated closure schemes. The other solution would be to try and move towards a city where motor traffic didn't dominate - where motor vehicles were only used where actually necessary. That would make it less necessary to be constantly fighting the traffic - with much-reduced levels of traffic and less of a presumption of priority, a more hands-off approach could work. I know plenty of people reading this will freak out at the idea of such a city, saying it's idealistic and completely inpractical, but other places have taken steps in that direction - and it works just fine, on the whole.
It's a shame such an ideal is considered impossibly radical even on urban75.
