I have no truck whatever with "common sense", which usually contains very little sense at all. I'll say it again - because helmets are irrelevant, it doesn't matter whether their decision is based on calmly evaluating all the research, keeping their mum happy, or not wanting to mess up their hair. It does matter if people see cyclists and what they see confirms or reinforces a belief that cycling is a dangerous activity (or simply one that requires a lot of special safety equipment), because it could make cycling less attractive in their eyes. This doesn't matter to Linf, because (as I said) he disapproves of cycling and doesn't want to see more cyclists enjoying themselves on the road. You'll just have to trust me on the last sentence.
Those extra cyclists you keep banging on about will most likely be existing car users who have opted to use a different mode of transport to get around locally due to the rising cost of running their vehicle.
You have to attribute them with the intelligence to make an informed decision over whether they feel cycling is safe or dangerous.
It follows logically for someone who owns and runs a car, to attribute that the safety rating will increase in a vehicle when the manufacturers have put in crumple zones, side impact bars, air bags, seat belt pre-tensioners, collapsible steering columns, automatic fuel cut out devices etc, etc. Many will also reason that the extra armour for a cyclist will help protect them (see how BMX and downhill riders dress for a collision, it does follow to a logical conclusion that there is merit in employing these devices to soak up the knocks)
They as regular drivers will see many cyclists on the road whilst on their travels, and they will draw their own conclusions on how close they see other vehicles pass the said 'example' cyclists. It is the close overtakes and turning left on cyclists which they will judge as being the dangers imposed on cyclists, and the level of RLJing and pavement cycling as to how they will consider other drivers will view them, and whether those other drivers will treat them with respect or contempt, and this is what they will see as the most positive or negative parts of taking it up.
I don't believe that having to stick a bit of polystyrene on their heads to participate in cycling will have a long term negative effect apart from with women who don't like messing their hair up by putting one one.
I've always considered that if compulsion came to pass, that people would eventually just suck it up - just as motorcyclists have done - helmet wearing has certainly saved a lot of lives in this group of road users, and this is at the core of my belief on this subject.
