Enlivened a long drive up to the Scottish Highlands along the M6 and M74 whilst my co-driver was at the wheel by surveying all the bridges we went under (power lines too). Surprising how many existing roads don't have a bridge marked - mainly the ones at the junctions are marked as bridges. I also found that in some places there was a misalignment between the motorway carriageways and the public GPS tracks.
So all you OSMers - time to re-survey British motorways? It'll sure alleviate the boredom!