The A46 has now been duelled between Cotgrave and Car Colston.
Today I have got some GPS traces of the section from Cotgrave to Margidunum (A6097) and have updated OSM (the section north of Margidunum is all interpolation - feel free to correct if you have better knowledge than I, especially the bits alongside, over and under the new A46.
The speed limits remain 40mph (which is a right drag on the nice wide dual carriageway even though it's coned to one lane) but heading north bound as the slip road starts at the Bingham junction you get two lanes of 70 mph travelling all the way though to Margidunum and beyond - you can now cover that section in a blink of an eye instead of the old nose to tail 90km/h (~56mph) drag behind the naughty lorries riding their speed limiters!
One rather odd bit is that between Margidunum and Bingham the old A46 is currently coned off to one lane (southbound only) and is the only way for A6097 traffic to join the A46 - i.e. the southbound A46 now has three lanes southbound over two carriageways where it used to have just a single lane! Not sure how south bound traffic leaves the A46 at Margidunum either (does this carry on down the old A46 from Car Colston?).
Rather fitting that the road which marked the original edge of the Roman empire now has a junction named after a long extinct Roman settlement (Margidunum) - although I wonder how many people will actually be able to say that?
Another interesting artefact of the junction naming is at the A52 where it crosses under the new A46 and interchanges with the old A46 - the villages of Saxondale (West) and Bingham (East) are either side of the junction - however the new "Bingham" junction is on the Saxondale side of the complex, and the old "Saxondale" junction is on the Bingham side.
Shouldn't be long now before the A46 becomes dual carriageway all the way from the M1 at Leicester to Farndon just outside Newark-on-Trent.