You can't drink and drive in one of these. If you are caught the car is impounded and the fines are the same as for licenced drivers. If you lost your licence for drunk driving and are tested positive your ban will be lengthened and you will be signed into a clinic for rehab. If you are caught without insurance you will also feel the pain.
Where things break down is in the countryside where everyone (including the local gendarme) knows everything about everyone else. There is some eye closing for local colourful characters.
Risk of accident 0,83 % for 2007. There were 150,000 on the road in 2012.
Following one in your car is no more painful than following English tourists towing their caravan through the beautiful French countryside, they go about the same speed