'Driving lane' has been used a couple of times in this thread.
So if someone is undertaking in the inside lane, thereby going fastest, is this then the 'fast lane?'
'Fast lane' is the incorrect term to use, they are, of course, all fast lanes.
Obviously. I meant outside of this thread in general use. When people use a term in a thread there's a tendency of replies to re-use to keep in context. I've never heard driving lane before. Can you find any reference to it out side of this thread? Seems to be a US term, that used to describe a lane you can drive in, or are driving in. Also a lane in a car park. Maybe its been shortened to just lane over the years.
Your query wasn't was "fast lane" technically correct. But why people use it. Being correct has got nothing to do with it. You use to hear it a lot more, but has fallen out of use. On average the outside lane is going to have the highest average speed, the inside the lowest. So its a sweeping generalisation.
Is there really any point in taking things so literally?