Graham - I had the same thought not so long ago and started this thread in the 'chat' section which led to a goodm debate.
http://forum.fellrunner.org.uk/showthread.php?t=6334
'Mind you they do reverse direction every two hours.'
I can't be bothered to read all the posts but are you talking about pensioners in Morrison's?
Which is where I spend all my time.... and the current state of my running bears it out!