Myth-Busting: Does constantly changing lanes get you there faster?
We’ve all been there, stuck in a line of ‘slow-moving’ traffic while cars in the outside lane are streaking past. So, does constantly changing lanes get you ‘there’ faster?
THIS IS ONE OF the trickiest myths we’ve explored and that because the answer relies on maths and some philosophy. You’d think because the answer is buried in cold-hard maths that it would be quite a simple answer, but it isn’t and that’s because mathematicians, scientists and philosophers are all of differing opinions.
Before we get to the maths and science behind lane changing and whether it really does get you there faster, it’s worth pausing for a moment to consider your own thoughts on the matter. Personally, I’ve done more than my fair share of commuting on major highways that are constantly clogged. And my own observation is that even if you’re breaking the speed limit and constantly swerving through traffic into too-small gaps you won’t get ‘there’ faster. And that’s because at some point there will be a choke point in the traffic and everyone’s progress will be halted…so, after your dangerous run through the traffic, you’ll still only end up a few cars further ahead than you would have had you stuck to the speed limit of the traffic around you. Or, if numerous studies are to be believed you won’t have.
A study by Nick Bostrom, a postdoctoral fellow in philosophy at Oxford University claims a slow lane is generally created by having too many cars crammed into it. Yep, we all agree with that. The flow-on of that is that if you’re in the slow-moving lane then you’ll spend more time in that lane and take longer to get to your destination. Yep, makes sense too. Bostrom’s solution to constantly changing lanes is to increase the diffusion rate and spread cars out evenly in each lane of the highway, but that goes against the road rules where on a two-lane divided road one of the lane’s is for overtaking only and not for spreading out traffic. And the same goes for a three-lane highway, there’s always one lane set aside for overtaking; intended for emergency vehicles to be able to rip down without traffic getting in the way.
So, increasing the diffusion rate is a fine idea but one that’s unlikely to happen because, well, drivers.
And then there’s a driver’s perception. A study by mathematicians Bryan Dawson and Troy Riggs at Union University in Jackson, Tennessee, suggested that a driver sitting on 90km/h and watching a car overtake them at 95km/h would wrongly assume that vehicle was traveling much faster than that, while the driver overtaking would assume the slower driver was going much slower than they were. The slower driver would, they surmised, see the faster driver and likely want to change lanes.
Similarly, Donald Redelmeier, a clinical epidemiologist at the University of Toronto and Robert Tibshirani a statistician at the University of Stanford, via the help of a computer and real-world observation, determined that the lane that appears to be moving more quickly actually ends up with the same average speed as that of the other lanes, even those that appear to be travelling more slowly. And that most people spend more time being overtaken than they do overtaking other cars.
For instance, they observed that while a car may overtake eight or so others and then return to the ‘slow’ lane, that car would then in turn be overtaken by other cars, creating the illusion that they’re going slower, rather than the more accurate observation that the overtaking cars are travelling faster than the speed limit, because of their perception of the speed of the bunched-up traffic. And then there’s the perception, they observed, that people tend to spend less time checking their rear vision mirror and so, when a driver overtakes someone the car behind them disappears, while when they’ve been overtaken the car that’s overtaken them remains “annoyingly” visible.
Redelmeier and Tibshirani also observed that constantly weaving in and out of traffic will increase the chance of a collision. Indeed, a recent study by VicRoads revealed that, on the Monash Freeway, during peak hour there are roughly 2000 lane changes, per hour, every kilometre. And that for every lane change a driver made, the risk of a collision increased six-fold.
So, while weaving through traffic on a race track might help you to get to the head of the pack, there’s no head of the pack when you’re driving on the road. And, based on the research, it’s likely that rather than getting anywhere faster by weaving on the highway, you’re simply fooling yourself via false perception and, at the same time, you’re increasing the risk of a collision.