I was riding south along the Kennedy Highway towards Atherton, in the tablelands west of Cairns in Far North Queensland, when I first saw the bicycle.
It was up ahead, on the shoulder of the other side of the road. Riderless, but pointing in my direction, and glowing white in the winter sun. The bike was firmly fixed to a cement base. A plaque trimmed with sea shells read, in part: "Always in our hearts: Lindsay Keith Cook."
A flick through my phone soon told me that Lindsay Cook – nicknamed "Chook" – was 47 years old when he was killed in a hit-and-run early one morning in 2010, while out training for a charity event. The driver of the vehicle has never been identified.
Travelling on a bicycle, you notice things more easily than when in a car, and are more inclined to stop and check them out. In a month of cycle touring around Queensland I saw several roadside memorials, heartfelt tributes to loved ones lost.
Some were in the shape of crosses, others displayed photographs, flowers and mementos. All bore testimony to the terrible toll our roads take on human lives. The most noticeable – and, for someone travelling on two wheels, the most poignant - were the two white bicycles I encountered.
"Ghost bikes" are said to have originated in St Louis, Missouri, more than a decade ago, as memorials that were also a way of drawing attention to the vulnerability of cyclists. They can also become a rallying point in campaigns for improved road safety.
One such example would be the bike placed on Brisbane's Moggill Road (above) in memory of Richard Pollett, a brilliant young violinist who was killed by a truck in 2011.
The driver was subsequently found not guilty of dangerous operation of a vehicle causing death, but Pollett's death sparked a push for a minimum distance passing law, which is now halfway through a two-year trial in Queensland. Similar measures have been proposed for New South Wales, South Australia and the ACT.
This week his mother, Patricia Pollett, told me she has not visited the site, but "I do ask after it, and know that it has an effect on people. I think the fact that it's a bike is a good thing and further reminds road users to be mindful of bicycle riders and their vulnerability."
In Melbourne, a white bike on Sydney Road where Alberto Paulon died in a "dooring" incident earlier this year was a focal point of a rally in his memory.
Thousands of cyclists rang their bells as they passed the site. "I'll never forget that sound," said the ride's organiser, Ed Hore of Australian Cycle Alliance.
As for the ghost bike I encountered outside Atherton, a ride called the "Chook Run" in Cook's memory has become an annual event, a road safety campaign was intensified and signage in the area was improved.
Cook's widow, Sharen, told me how the community rallied around the issue. "It's really amazing – that silent message, and how important it becomes to a lot of people," she said.
One interesting aspect of ghost bikes is that there is no set procedure for their creation. Rather, they are a spontaneous response to grief and loss, by an individual, a family, a town or a community of cyclists.
Some might feel that they bring too much focus on the possible dangers of cycling, and might discourage people from taking to two-wheeled transport.
For me, they are a reminder that there is so much more to be done regarding safety for bike riders, who are also too often the target of stereotyping, irrational anger and even vilification.
If the sight of a ghost bike helps to remind that a moment's inattention, impatience or carelessness can have devastating results, that's a good outcome for all of us.
Have you encountered any ghost bikes on your rides? What is your reaction to them?
Fairfax journalist Michael O'Reilly will join Al Hinds and Anthony Tan for an SBS Cycling Central podcast released every Thursday afternoon during the Tour de France.