Already commonplace...
Unfortunately necessary due to retards of most ages not being able to understand the Green Cross Code, or have the brain power to implement it. Perhaps the government should spend money on rerunning the 1970's campaigns.
My annoyance of this comes from where I work - roundabout city, aka Milton Keynes.
For those lucky enough to never have been there, Milton Keynes is a large, diverse, sprawling town that has the widest range of inhabitants. Some of these inhabitants obviously have recently evolved from pond life.
The planners of MK have done a fantastic job of planning the town, keeping cars and pedestrians/cyclists seperate for safety reasons, and allowing good traffic flow. MK is built on a series of North/South and East/West roads, forming a grid. Some are single carriageway, most main grid roads are dual carriageway. To keep pedestrians and cyclists safe from traffic, there is a seperate system of good 'roads' purely for them, called Redways. These Redways have bridges or subways wherever they cross a grid road. Therefore, the gridroads were all at National Speed restrictions (60/70mph)
Ideal? Yes, absolutely. It works very, very, very well, and should be used in all large towns.
Problems? You bet. The planners didn't comprehend quite how stupid the offspring of some of the more incredibly stupid inhabitants could be. So, in certain parts of town, you have idiots, who to be fair lack the brain power to know that stepping out in front of a bus will hurt, step out in front of moving traffic with the obvious consequences. There are also far too stupid to use the Redways. This seems to be a particular problem in certain parts of town - near the 'no-go' areas where the council tend to put the more problematic families.
The council's solution? Rather than tackle the real issue, lower the speed limits to 30/50mph. A car hitting someone at 50mph is going to kill these people equally effectively as hitting them at 70.
Now, if I was in charge of the council there, I would keep the speed limits at the national levels. Yes, people stupid enough not to use the Redways will die, but some of these estates need a better gene pool anyway

Anyway, now I've upset most of our North Bucks members.......