We've a few places where helmets have been made compulsory, so the easy way to see if it's actually worth doing is look there to see what has actually happened in those places, rather than assume what might happen elsewhere.

And what we see is no cost benefit and no reduction in serious injury rates for cyclists but a reduction in cycle numbers (which suggests more polluting, congesting journeys in lieu). That's what actually happens, so voting yes, however well meaning, is a public health own-goal.

We need to stop assuming what we want to happen and would be nice if it did happen, and look at what does happen. And the real-world record of cycle helmets for road-going cyclists getting from A to B is they are no real help, but do put people off a remarkably healthy way to get around.