I make many very long journeys across France each year, am very familiar with my planned route (Calais - Avignon) but use the nav. system for advice on ETA and alternate routings if needed.  I am finding that on many journeys the route will be changed with lengthy diversions as the TMC has thrown up a road closure.

 

It is almost always a service area entry or exit slip road which is actually closed, but the system is interpreting it as the actual motorway/autoroute has been shut so computes an alternative route - which would sometimes add 100km / 1 hour or more if taken seriously.  I just ignore it unless it also on the radio traffic channel or overhead gantries but Is this a common experience? My last trip it happened 3 times.  Any way to fix it?     

1 hour ago, slast said:

Is this a common experience? My last trip it happened 3 times.  Any way to fix it?     

It's happened to me several times in France, usually because the TMC data is way out of date (over a year in one case), so like you I just ignore the rerouting and go the eay I want to go until it's obvious that the road is actually closed.

Thanks for that - where does the TMC data come from then? These changes are occurring when I am en route - is it because I am just getting into range of a particular radio station?  

39 minutes ago, slast said:

Thanks for that - where does the TMC data come from then? These changes are occurring when I am en route - is it because I am just getting into range of a particular radio station?  

TMC data is transmitted over many different FM stations, not sure where the source is in France, but they clearly don't properly maintain accurate data!

 

Wikipedia suggests the TMC data in France is provided by Mediamobile https://en.wikipedia.org/wiki/Traffic_message_channel#France