This route in north-eastern France runs through a former coal-mining area (the Bassin Minier, mining basin). It’s a patchwork of minor roads and former mineral railways, with the balance roughly 60% off-road.
Though unlikely to attract many tourists as a route in itself, it’s a useful connection between EuroVelo routes 3 and 5, and not without interest for enthusiasts of industrial heritage. West of Douai it’s not yet signposted and you’ll have to find your own way on roadside paths and back streets. You could usefully combine this with RAVeL routes in Belgium to make a circular tour.