Mark
I asked a similar question last year, answered by Gilles.
In Gilles absence, I have been back into the old site and pasted the reply below, hope this helps.
Some of the follow up was quite good, it wassuggested to get the boys to wear a white tee shirt and paint a black line across the chest, or two black lines for the full harness effect.
Andy Z
PS I think I've got SARS, or at least some other horrible flu bug. My chest's that bad, I'm having difficulty smoking.
FROM Gilles 2002: "Someone asks my science ??
You can't have someone (one or two or more) in the back of your van.
It's one guy per seat as mentioned on your vehicle card, specifications book,...
If you want to transform your van to a bus, I hope you can ad optional seats. Most of vans have fixations to do it.
Concerning seatbelts, you have to lock it if you've got one. The obligation in France starts in 73 or 71 and isn't retroactive. So if you've just 2 seatbelts for 3 seats just lock the twice.
What's the risk if the gendarmes catch you? Probably just a fine (don't ask me for the amount).
So you've three solutions:
First, buy and fix optional seats if your van is able.
Second, give blankets and pillows to the backside guys to hide them when you see law enforcement authorities.
Third, add a horse trailer to host them. They will sleep well on the straw, (ok it's dangerous for cooking breakfast, but I prefer Hot Rosbeef !!!!!) and straw will make a perfect chill conservator for beers, not included the huge volume of beers and stuffs you can bring with you. You can bring your pony with you. It'll always better than a simple bike to make trips around the circuit.
Gilles