There was an interesting little story a few weeks ago in the London Telegraph about how GPS systems are causing traffic problems on the popular tourist Ring of Kerry trail between Killorgon and Kenmare.
Apparently, traffic traditionally travels in a one way fashion counter-clockwise between Killorgon and Kenmare, but GPS systems are telling drivers to go clockwise instead. When tourist coaches traveling one way meet trucks coming the other, traffic bottlenecks start appearing on the narrow trail.
The Killarney Town Council, the Telegraph says, wants GPS manufacturers to change their instructions to drivers. GPS manufacturers said they are open to the suggestion, but also said that the local councils have to let them know of these "unwritten" rules.
Other GPS related related stories are here and here.
