Hollins, I live very close to the location and use that area every single day as do my wife and children who walk that way to school.
Nowhere in my post did I say that Church Lane was built for that kind of traffic. None of the roads in Marple were built for the traffic they have now. In fact, when Marple had far fewer cars, Church Lane was two way traffic. The speed bumps on Church Lane are nothing to do with the current supermarket. Anyone who lived near the road before the speed bumps will recall cars speeding up Church Lane with little regard for anyone's safety and when they were added it reduced the speed, and therefore the risk, considerably. Now, of course, they speed up the higher part of Church Lane instead.
As the size of the convenience store increased and became a small supermarket then clearly traffic needed to be managed better. It's obvious that the amount of traffic going through the site has increased significantly since the new store was built which is why an attempt was made to route it by adding the no entry/exit signs. Drivers who ignore them, whether they're just "suggestions" or not are behaving inconsiderately and putting other people at risk. Just because drivers disagree with a sign that causes them minor inconvenience is no excuse for ignoring it.