Every year TomTom produce a report about how much worse congestion is getting in Auckland, and every year the media lap it up – usually without looking at the flawed methodology of the report. So it was the NZ Herald yesterday:
Auckland’s roads are so congested commuters are spending an extra 45 minutes a day – or four working weeks a year – stuck in traffic.
A new report has revealed the country’s congestion is now worse than Hong Kong with the time spent on Auckland’s roads doubling in the space of three years.
TomTom has released the results of its Traffic Index 2017, an annual report about traffic congestion in cities around the world.
Auckland is ranked as the 47th most congested city on the planet, worse than Hong Kong, which has a population of 7.2 million.
Auckland’s level of congestion has risen from 33 per cent of extra travel time in 2015 to 38 per cent in 2016.
Drivers in New Zealand’s biggest city now spend an extra 45 minutes each day stuck in rush hour traffic, the equivalent to 172 hours, or four working weeks in a year.
As we’ve noted quite a few times before, the way in which TomTom derive their congestion “scores” is pretty meaningless because it focuses so much on comparing travel times between peak and off-peak, rather than actually looking at the overall average travel times for different cities.
We’ve unpicked this methodology before, but perhaps the best explanation of how stupid it is comes from Jarrett Walker, looking at “Urban Mobility Report” produced by the Texas Transport Institute using a very similar methodology to the TomTom report:
The technical core of the argument is simple. TTI’s Travel Time Index, one of their more quoted products, is a ratio of peak congested travel times by car against uncongested travel times by car. In other words, travel times are said to be “worse” only if they get much longer in peak commute hours than they are midday.
This ratio inevitably gives “better” scores to cities where normal uncongested travel times are pretty long — in other words, spread-out cities. Here’s the CEOs’ critique of how the TTI compares Charlotte and Chicago:
Now it seems complete nonsense to say that Chicago, with an average travel time of 32.6 minutes has worse congestion than Charlotte, with an average time of 48 minutes – but that’s exactly what’s happening here. Furthermore, the methodology completely ignores how an increasing proportion of trips taken by rapid transit, walking and cycling aren’t affected by congestion. Jarrett Walker again:
The journalistic spin that TTI itself recommends is that non-car modes matter only if they reduce congestion, and that congestion remains the primary measure of urban mobility.
What’s more, TTI’s suggestion that public transit directly reduces congestion is actually quite fraught, and many transit experts, including myself, steer away from it. Transit certainly creates alternatives to congestion for individuals, and the resulting benefit to individuals can be aggregated to describe society-wide improvements in both productive time and personal/family time. But those calculations are much more clear and direct than any “transit benefit to congestion” overall. That’s because newly freed, high demand road space tends to induce new car trips.
Most transit projects are not trying to reduce congestion, or not all by themselves. If congestion reduction is your goal, you need a combination of transit and market-rate “decongestion” pricing for motorists. For most advocates of transit in the context of compact sustainable cities, the goal is not to reduce congestion but to give citizens options to liberate themselves from it.
This is why it’s so important we invest in a greater range of transport options and particularly ones that are able to move a lot of people reliably and not affected by traffic congestion. Sure not everyone can or will want to use them but we’ve seen first hand in Auckland than when offered good options, many will flock to use them.
Perhaps the most useful way of using the TomTom report is not so much comparing across different cities – for the reasons best illustrated above – but more to track the same place over time. In that respect Auckland is seeing a pretty big increase in congestion over the past few years, up from around 100 hours a year to 170 hours a year. This is a pretty sad indictment, given how much focus the government has on reducing congestion and how much money they continue to sink into building more roads.
It will be interesting to see next year’s results and whether completing the Western Ring Route has made things better, or worse.