Next time you are stuck in heavy traffic on a Victorian freeway, you might want to think twice before changing lanes to get ahead.
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New research by VicRoads reveals the crash rate on Melbourne's freeway network surges sixfold at peak hour, and many of the collisions are caused by our compulsive lane-changing habits.
While Melbourne drivers have no hang-ups about weaving in front of other vehicles to try and inch ahead, we are less generous when others seek to do the same to us. It's a selfish instinct that increases congestion and the likelihood of a crash, the research suggests.
VicRoads has studied the correlation between crashes and lane-changing behaviour on Melbourne's busiest freeway, the Monash.
During peak hour there are typically about 2000 lane changes on each kilometre of the Monash Freeway.
In Melbourne, 100,000 new drivers and a similar number of vehicles join the road network each year, leading to an ever-increasing amount of traffic, which is making driving a more complex task than it used to be, VicRoads manager, network optimisation John Gaffney says.
In his research, Mr Gaffney has found that in the morning peak, the rate of crashes on Melbourne's managed freeway system is about five times greater than in off-peak times and about six times greater in the afternoon peak between 4pm and 5pm, the worst time for freeway crashes.
"When a freeway is reaching capacity and running heavy, which is now most of the day, there's typically 2000 lane changes per hour, every kilometre, and the driver's capability to handle that with close headways and gaps, is increasingly more complex than it was back in the 1970s," Mr Gaffney said.
"So you start to get an idea on just one carriageway, how many chances of collisions occur. And what is happening on our freeways, is people close up so they don't let other people in – but they don't realise that if everyone is making five or more lane changes, they have to show that courtesy, because they will need that space themselves for the freeway to work."
There is a delicate science to keeping traffic flowing that has led VicRoads to change the way it manages Melbourne's freeways.
For many years the authority sought to get as much traffic as possible onto the freeways, only to learn that this creates congestion that slows down every journey by 20 to 40 per cent.
Technology such as ramp metering, which controls access to the freeway, aims to create a sweet spot of a 50-metre buffer between moving vehicles, which maximises traffic flow and leaves enough room for drivers to safely change lanes.
But VicRoads' efforts to exert greater control of traffic flow have been controversial at times.
In 2015 it said that the speed limit on the Tullamarine Freeway and CityLink would be permanently cut from 100 km/h to 80 km/h once the current widening project is complete in 2018, only to back away from the plan the next day following an outcry.
The authority's approach to managing Melbourne freeway traffic is gaining influence in the US, where states including Utah and Arizona are trialling it on their freeways.
Mr Gaffney's work on the link between congestion and collisions is set to take him to Europe this year on a Churchill Fellowship, awarded by a trust that funds overseas travel by Australians to conduct research they could not readily do here.
He will meet with vehicle control engineers, physicists, road safety experts and behavioural psychologists who are studying the human brain, and how much it can handle before it makes errors.
"What I hope this opportunity will lead to is new ideas in how we can manage motorways better, from a traffic point of view as well as a safety point of view," he said.
This story, Report reveals the common causes of freeway collisions, first appeared on The Age.
