Read a comments thread on a cycling article, and you'll often see somebody complaining about cyclists who ride two abreast.
To wit: 'Why on earth do they do it, instead of riding along the left edge of the road in single file?'
Riding abreast is a favourite technique for cyclists travelling in a group, where participants take turns to lead the bunch, spending the extra energy required to force a path through the air resistance up front - then dropping to the back of the group and recovering in the slipstream created by the new leaders.
With a fellow rider at one's shoulder, it can be a companionable and speedy way to travel, with predictable and disciplined riding necessary to prevent accidental contact that could cause a crash.
A safe option
The first thing to note is that cyclists are legally entitled to ride two abreast and must stay no more than 1.5 metres apart.
More importantly, it's often the safest way for a group of cyclists to travel - with the added benefit that it can make it easier for cars to pass.
"If a bunch ride is running in good, close formation they almost act like a vehicle themselves," says Alexandra Bright of Cycling Australia, the peak body for cycling clubs.
"And it's actually safer to be together than to be strung out, because a car can simply pull out and go around that group as a whole, rather than having to pass multiple individual cyclists."
As the video attached to this story shows, a line of two-abreast cyclists is half the length of a single file of riders, meaning the driver has to spend less time on the opposite side of the road when overtaking.
At the same time, riding two abreast on a narrow road can prevent a driver from trying to squeeze their vehicle past a line of cyclists in the face of oncoming traffic - and running the risk of crowding a rider off the road.
Douglas Kirkham, the president of Dulwich Hill Bicycle Club, says visibility is another benefit: "In a bunch you're far more easy to see by another road user, and then that road user can make allowances to go around you, slow safely, or whatever it might be."
Common sense approach
But both point out that there are many instances when it's more practical - or polite - to move into single file.
"The road rules are that you can ride two abreast, but I think at all times it helps to use common sense and to single out when it's preferable to do so," says Bright.
Kirkham agrees: "There are certain portions on our regular ride, when it's later in the morning and there are a lot of parked cars, where as a ride leader I like to organise the group into single file to allow traffic to flow past us," he says.
"There are places where we can do that because it's safe for us to be single file, and we can double up again another 500 metres down the road. I think there are times when it's got a great deal of value."
Responding to danger
One of the challenges to mutual understanding between cyclists and drivers is that riders will often see dangers or impediments that are of no consequence to motor vehicles - such as pinch points, uneven surfaces and potholes, or road shoulders that disappear.
Parked cars are an especial hazard on multi-lane roads, forcing a bunch to weave in and out of the left-hand lane - on Melbourne's Beach Road, where there are more than twice as many bikes as cars on weekends, a clearway has eased tensions and conflict.
I've been on some great bunch rides but I'm not a regular because I'm not very good at getting out of bed. Almost all groups head out at first light, when the roads are empty of cars.
If you encounter a group at 10am, chances are they've been on the road for hours already - and they're possibly being held up by cars as much as they might be impeding motor vehicle progress. After all, cars are built "two abreast" - which doesn't change when they have just a single occupant - and can certainly take up a lot of room.
As for the contention that roads aren't for recreation, well ... consider the traffic jams on coastal roads in summer. Going to the beach is a recreation - and the road is being used to facilitate that activity.
Roads are for people
The truth is that roads aren't for vehicles, they're for people - and we all pay for them through general taxes and council rates.
Sure, there can be frustrations - bunches that are ramshackle or inconsiderate, roads that get crowded, drivers who get delayed - but the benefits to public health, both physical and mental, surely offset these distractions.
In fact, just thinking about it has made me want to go on another bunch ride. Time to set that alarm clock.
Let us know your thoughts in the comments section. Submissions will be carefully moderated and only those addressing the topic will be considered for publication.
Fairfax journalist Michael O'Reilly has written the On Your Bike blog since 2011. He has won a Cycling Promotion Fund media award and is a regular voice for cycling on radio and television.