We have a Bip&Go toll tag on our motorhome. On the motorways with the overhead gantries it has worked fine in Portugal. But we tried going through one of the green lanes on the motorway and the tag didn't beep either at the entry toll or the exit toll. Big signs up saying you will be fined if you use the toll incorrectly. Does the fact it didn't beep mean it's not valid for these lanes, in which case I'm a due a fine? Or does it register the presence of the tag but just not beep?