As a cyclist in Paris, yes, I'd say the presence (and domination) of cars is a BIG reason I feel less safe. I have friends from other cities who grew up biking but who don't dare get on one the excellent bikeshare Vélib bikes to get around because they're afraid of being hit. But cars are just one piece in the puzzle; I think what's worse is the psychological atmosphere: the stress, the having to always be on the lookout and, oddly, the lack of civility.

I've approached trucks and cars parked on the bike lane to ask them if they could move just a little to the so bikes don't have to swerve around them and enter the flow of car traffic. I do so politely, making sure to not adopt a defensive/aggressive attitude. In a few rare cases, the driver had been genuinely unaware and apologized and moved. In most cases though, I'm insulted and told, "vous me faites chier !" (something along the lines of "You're pissing me off!"). I was once even told by a genleman on a scooter that, "If you want to ride your bike, why don't you just go to the countryside?"

If you're on a bike, cars, scooters and motorbikes will constantly remind you that you're not welcome. Try explaining to a car that he's parked on the "sas vélo", that little space reserved for bikes in front of traffic lights. Or explaining to cars that when they turn right and through a bike lane, that it's common courtesy to signal the turn (instead of suddenly turning and shouting at bikes for being in their way). It's a problem of education, too.

Cyclists aren't all innocent, either. I've seen people on bikes not stop for pedestrians even when they have right of way. Pedestrians, who are understandably annoyed and probably used to no one looking out for them, also do stupid things like cross when it's red even as they see a bike approaching fast downhill. (This actually happened to me; she apologized when I had to slam my brakes, as did the car behind me. What was odd was that she actually stopped before crossing, saw that the light was red for her and green for cars and bikes, that we were approaching and started crossing anyway. And this isn't an isolated incident, I experience this at least two or three times per week).

So, it's a very unhealthy environment where everybody feels no one respects their rights. But cars are by far the biggest reason Paris feels unsafe (even though it really isn't once you get the hang of it).

I ride without a helmet but recently got a Hövding (the portably bike airbag from Sweden) to test in the city and wrote a review of it[1]. Mine actually went of accidentally, but I thing they're very, very promising. Not least because of how much more effective they are at oblique, non-perpendicular impacts.

[1]: http://www.neustadt.fr/reviews/testing-hovding-invisible-hel...