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On approach, it didn't look much like a roundabout, although this wasn't helped by the fact my sat nav app didn't register it as one.

"My Sat Nav took me all up country roads. I stopped a guy in the narrowest lane I've ever been down," he told BBC Radio Somerset.

Earlier analysis by transport consultants - using in-vehicle sat nav data - also found a reduction, although this included some roads where drivers would be forced to slow down naturally.

He told BBC Scotland News he had not driven in the city for about 10 years, but his sat nav had not picked up the road changes.

A barrier is to be installed at the top of a notorious street in Edinburgh after sat nav errors repeatedly directed drivers down a set of steps.