Sydney's plan to adopt Boris bikes can't come soon enough.



The most notable legacy of London mayor Boris Johnson, a bike share scheme makes the city delightful for visitors, and a little less of a grey, crowded place to live for locals. It's cheap, safe, and quick.



Last time I was there, the bikes stopped Trafalgar Square from being a rammed tourist haunt to avoid. Instead, I found a bike stand, paid the fee and soon was on the street, passing frustrated passengers in black cabs, whizzing from the National Gallery down The Mall to see The Queen, or as far as it's possible to whizz on machines with such fat tyres.



It's both a serious and fun way to get around, making short trips much faster than car or tube.



More than 400 cities now have bike sharing schemes, and Sydney's welcome plan to join them means it can avoid the screw-ups that have made the Australian examples so disappointing.



Sydney Lord Mayor Clover Moore told the Australian Financial Review last week her council is planning a bike share scheme, once there were enough separated cycle ways in the city. A pilot is mooted before 2020. Bring it on.



But if Sydney is to match the success of the scheme in London, rather than the under-used pretenders in Brisbane and Melbourne, there is one clear difference between those that work and those that don't.

Helmets. We will have to ditch the lids.



Helmets aren't required in London, or Paris, or New York, or most cities which have added cycles to the public transport mix. You don't need to plan to use them.



Allowing such spontaneity is not the antipodean way. Both Brisbane and Melbourne inflict the helmet rule on their bike share schemes, with making them far less popular than they could be.



According to figures released last year, in summer the Melbourne bikes are used less than once a day. That figure is far lower than in New York, where each bike is used about five times a day.



For all the hard, welcome work the City of Sydney has done making biking to work viable for city workers – which it has in spite of ferocious and moronic opposition – a cycle share scheme will need an exemption for helmets if it is not to be a well-intentioned fizzer.



Making occasional riders of big-wheeled velocipedes buy disposable helmets before they can trundle from Martin Place to Circular Quay or Barangaroo would condemn a good idea to a bad reality. It risks instead becoming a wastefully expensive repetitive piece of footpath art.



A study published in Transportation Research in 2012 found the two largest deterrents to people using Brisbane's cycle scheme were that helmets were hard to find (36 per cent) and not wanting to wear one (25 per cent). Each of them alone were far more off-putting than the weather, cost or safety.



In Melbourne, wannabe cyclists have to find a helmet before setting off either by hoping to find one left with the bike, including the sweat from previous user, or scour nearby convenience stores for a $5 one.



As Arnold Schwarzenegger knows after a run-in with Melbourne police earlier this year, riding helmet free risks being stopped and fined by a constabulary with evidently little else to do. (Schwarzenegger escaped with a warning.)



But if there's one place it should be relatively safe to ride without a lid, it's in the central city. Traffic is slower, and in Sydney there are now, finally, more separated bike paths being built to reduce conflict between driver, rider and pedestrian.



For the Sydney scheme to work, we don't need to resolve the intractable debate over the utility of helmets by ditching the general rule, at least not as long as some drivers behave so abominably towards those on two wheels for doing nothing more offensive than carbon-free commuting.



Instead, it would be easy enough to exempt most streets in the central city from helmets to give the scheme a chance. The zone could stretch beyond the CBD from North Sydney to Redfern and Waterloo in the south, from Centennial Park and Paddington in the east to Sydney University and Newtown in the west.



It would establish central Sydney as an oasis for spontaneous bikers, and make it a little quicker and a little more fun to get around.