Cycling might be a generally controversial subject in Australia, but there is one particular topic that can generate strenuous disagreement among avid cyclists and non-riders alike.
Mandatory helmet laws for cyclists.
Brought in more than a quarter-century ago, the laws have long fuelled arguments: yes, helmets prevent injuries, but how many people are discouraged from cycling by making them compulsory? What is the net effect of the laws on population health?
As Craig Richards, CEO of Bicycle Network, puts it: "What I hate most about the mandatory helmet debate is that it's hard to have the debate."
Nevertheless, Australia's largest cycling organisation, with 50,000 members, is grasping the nettle. This month it launched a policy review process that may result in it changing its historical support for the laws.
So why take on the challenge?
Richards told me: "I believe it's our responsibility as an organisation that represents bike riders, and whose purpose is to get more people riding, to review the helmet laws … it's our duty to look at these things regularly, fearlessly and intelligently."
The issue "sparks up and down but it's always there and I think part of the reason why it causes such angst is because people on both sides are very set in their views".
The review has been initiated with an online survey that polls members and non-members alike on their general riding habits and opinions about helmet use.
"To conduct our review, we'll be asking ourselves what's the impact of mandatory helmets on four key things," the survey states: "The essence of bike riding: freedom and convenience? The number of people riding? The number of crashes? The severity of injury if there is a crash?
Once the survey is completed, the organisation will invite comment on helmet laws from a range of experts, to be published through the course of the process.
Finally, Bicycle Network will conduct a review of scientific literature on the subject, and look at case studies, including places where laws were implemented but later repealed, before making a final decision on whether to change its helmet policy, or maintain the status quo.
'Relative risks and benefits'
The organisation isn't the only one to tackle the issue of helmet laws in recent years.
In the ACT, an expert will be "engaged to examine the relative risks and benefits of changing the requirement to wear a helmet in certain low-speed environments" as part of their Road Safety Action Plan 2016-2020.
In 2015-2016, a Senate inquiry into bicycle helmet laws held two days of hearings in which experts from both sides of the argument gave opinions and evidence. In an interim report, the committee recommended that a national data set be established and used to assess mandatory bicycle helmet laws; the inquiry is now lapsed.
In 2013, a Parliamentary Inquiry in Queensland recommended that people over 16 be allowed to ride without helmets in places such as bike paths, roads with speed limits of 60km/h or less and when using share bike schemes. (The proposal was rejected.)
In Brisbane, Deputy Mayor Adrian Schrinner has repeatedly argued against helmet laws, while Fremantle mayor Brad Pettitt has also called for an easing of the rules.
Meanwhile, organised "helmet free" rides have been held in metropolitan cities, including one in Melbourne in March that, by my reckoning, drew more media coverage than a naked bike ride (in which riders mostly wore helmets) held the next day.
Nevertheless, government agencies and health and safety organisations remain firmly committed to the status quo, with Professor Rebecca Ivers of the George Institute this week warning against any change to the laws.
It's always worth remembering that Australia is an outlier on this issue.
As the first country to get bike helmet laws, it must have seemed that we were in the vanguard of a global movement, following on from our nation's pioneering adoption of seatbelt laws.
New Zealand fell into line, and then … not much more. At present, several Canadian provinces, a handful of US local jurisdictions and a couple of small nations appear to be among the few places that also enforce blanket all-ages helmet laws.
Despite the rules, compliance and enforcement can fluctuate wildly across our island continent.
And even the laws aren't uniform. In the Northern Territory, adults can legally ride unhelmeted on separated bike paths and footpaths.
The NT's special status is one area Bicycle Network's review will focus on, says Richards.
"It has the highest proportion of bike riders in Australia, according to the National Cycling Participation Survey - although there are probably a lot of reasons for that, it's hard to isolate it to one," he says. "Darwin and Alice are bike friendly in many ways."
If Bicycle Network does alter its policy, it won't be the first time in recent history that they've changed their stance on a controversial issue.
After previous scepticism about minimum distance passing laws, the organisation changed its policy following a survey of its members and now campaigns for the introduction of the laws in Victoria.
Bicycle Network says more than 18,000 people have already taken its helmet survey, and the review process should be completed by April next year.
Fairfax journalist Michael O'Reilly has written the On Your Bike blog since 2011.