London’s Ultra-Low Emission Zone prevents the most polluting vehicles from entering the center. A congestion charge applies to all vehicles, to reduce traffic volumes.
A global city ranking
If these variables were considered, we wouldn’t be comparing reality, we wouldn’t be showing the truth of what is actually happening on the ground. While it might allow us to rank every city in the world with what seems like more standardization and some comparative fairness, the truth is it wouldn’t be an inaccurate data set.
Taking a different approach; it would be possible to rank cities by which one has improved its congestion situation the most. This would allude to some kind of “most improved” rank, comparing cities to themselves and then ranking them based on that. But even then, as Marchant points out, it would not necessarily yield a clear or accurate picture of the state of global congestion. Some cities are far more concerned about congestion than others.
“We talked about the Traffic Index rank, and we said we could create the ranking based not on the worst performing city in terms of congestion but then base it on which city has improved the most,” Marchant explains. This might sound preferable to some, but on further inspection it’s still not the silver bullet critics are looking for.
If TomTom were to rank cities based on which has reduced congestion the most compared to last year, it would unfairly favor the cities that were hit with the most stringent and extreme lockdowns, Marchant explains. So, as with trying to factor the impact of lockdowns, this approach would do the exact opposite and give lockdowns excessive influence over the Traffic Index’s rankings. It would become a ranking of simply what cities were hit by the pandemic the hardest, no longer is it a measure of traffic.
TomTom’s Traffic Index data scientist, Anna Nowak, adds more detail: “The rank has always been the same, we provide the number for the full year. That number doesn’t tell the whole story, but it tells you something to start with.”
On TomTom’s Traffic Index homepage, more than 400 cities around the world are ranked in terms of congestion. This serves as a starting point for readers, an overview from which to dive into, Nowak tells me. There are plenty of filters that readers can use to organize the data by what context they feel is most appropriate.
Indeed, looking at the global ranking, there are some trends that present themselves, for example, the most congested cities tended to reopen quickly after lockdown, have poor public transit, regularly experience bad weather, don’t support cycling all that well and are incredibly car-dependent.
“People can argue that we’re comparing cities that have no snow with cities that have four months of snow,” Nowak says. “That can be argued indefinitely because there is always going to be some kind of difference, it’s very difficult to account for.”
The fact is, all cities are different, all responded to coronavirus in their own way. To try and account for differences would fail to demonstrate the uniqueness of each location and how its traffic is impacted by its own policy, geography and global events. As one of our other blogs on the topic alluded to: TomTom Traffic Index is a barometer of social activity, which is to say it takes a ‘temperature reading’ and reports it.
For that matter, when we’re considering the differences in weather around the world, we don’t try to compare the average temperature in Norway to that of Egypt. Why? Because we know they are two very different places and it’s basically impossible to even begin to attempt to compare them. There’s plenty of self-evident context as to why that’s the case.
A global ranking is a useful way to quickly show how cities stack up against each other, to provide a springboard for readers to dive into the data from. But just because a city goes up (or down) in the ranking doesn’t mean that its level of congestion has improved. If we want to draw specific conclusions, we need to look at the individual city specifically.
Traffic changes over time
There is value in showing how traffic in one city has changed over the years. It lets us see how one government’s approach to lockdowns affected traffic, and it also allows us to compare the impact that changes in infrastructure and policy have – providing a sort of before-and-after picture.
