I mentioned a few days ago that this weekend is the national recumbent bike weekend in the Netherlands.
Contemporaneous with this, there's a slightly worrying story from Australia. Apparently there is a proposal to make all recumbent cyclists in the country have a flag on their bikes in order to "increase regulation and legal compliance of human powered vehicles." As the linked article notes, "this proposal appears to be based based on spurious and anecdotal experiential demand."
Australia is already one of the very few places where cycling helmets are compulsory, and this is another step along the same lines. The message would seem to be that "cycling is dangerous". It's a mystery to me why Australians, who to much of the world seem to have rather a "rugged" reputation should seemingly be scared of bicycles and leading the world in such scaremongering. However, Australia's cycling rate is one of the very lowest in the world, so if the intention is to marginalize cycling then I guess it's working.
Bicycles are in themselves extremely safe. It is automobiles which kill as many people as wars, not bikes. Recumbent bikes may actually be rather safer, in that falls are often from a lower height, and if you fall, you usually land on your backside. In the case of a velomobile like my Mango, you're completely surrounded by a shell which protects in the case of a crash.
I'm not aware of any real evidence that recumbents are less visible than other bikes. Indeed, my experience on first riding one on the roads in the UK was that more drivers noticed me, and these would give me more space on the road. Sometimes dramatically more space. I certainly don't believe that my 2.5 m long bright yellow Mango would be more visible if only for a 15 cm long flag, and my brief experimentation with a flag on a two wheel recumbent (in the photo above) lead to a conclusion that from behind, the flag was the least visible part of the bike.
I don't believe that there is actually any reliable evidence one way or the other about relative safety of recumbent vs. other bicycles, so punitive laws against a particular group of cyclists are difficult to justify.
It's issues like this that require cyclists to behave as a whole. It does no good for different "tribes" to develop. It's no good for racers to disregard the interests of mums with kids on bikes, or for "slow cyclists" to distance themselves from sport cyclists. Indeed, it doesn't even help for cyclists to distance themselves from drivers. If we're to see a dramatic increase in cycling around the world, people who drive now are future cyclists. These kinds of issues affect everyone. "Them and us" helps none of us.
The photo is of my old Pashley PDQ on the top of Shap Fell, part way along the one tour when I did use a flag. It was less visible than the basket. Of course, if you prefer to ride with a flag, that's your own personal choice. Good luck to you.