Todd Littman of the Victoria Transport Policy Institute has put together a really useful critical analysis of the way we measure congestion and how this affects the general approaches taken to reducing congestion – typically seen (especially when undertaking cost-benefit analyses of transport projects) as the main justification for transport expenditure. The article is a fairly easy read, if somewhat lengthy, so I won’t go through all the details. Here’s the abstract: To keep this post from getting too technical and detailed, I’ll largely focus on the pictures and graphs that are in the article. This is a particularly relevant graph, because it means that unless our transport demand modelling has been updated to take account of the pretty radical change to traffic volumes (this is the USA, but we’ve seen similar trends in New Zealand) in the past few years, chances are we’re going to be enormously over-estimating traffic volumes (and therefore congestion) in the future. There is a real danger of failure to see change, even after it has happened, by people who have spent their careers under one orthodoxy. And I believe that is what is happening now at the MoT, if the reports I hear are true, of officials there arguing that there is no point in changing policy just because of recent trends. Well how long do ‘recent trends’ have to continue before they become the relevant? 5 years? 10 years?: Some of the dip is obviously due to the economic situation over the past few years, but other aspects might be more structural – relating to demographic change, changing land-use patterns, significantly higher fuel costs and general cultural change. Littman’s article notes that, should this down-turn in traffic volumes prove to be long-lasting and structural, it really changes the way we approach the issue of congestion in the future:
It made sense to invest significant resources in roadway when the basic roadway system was first developed and automobile travel demand was growing rapidly. During that period highway projects provided high economic returns, consumers reaped large benefits, and there is little risk of overbuilding roadway capacity since it would eventually fill. But once the road system matures, so there are high-speed highways connecting regions and a well-developed network of paved local roads, the marginal benefits of incremental roadway expansion tend to decline.
Transport planning and financing practices will need to change in response to reduced growth in vehicle travel demand and congestion problems, and increasing demand for travel by alternative modes. This will require reducing emphasis on congestion problems and roadway expansion and increasing emphasis on other planning objectives and other types of transport system improvements.
Most of our long-term thinking is still based on the assumption that traffic rates will grow and grow. To an extent, in a place like Auckland where the population is growing quickly, that is likely to be somewhat true – but it seems reasonable to expect that per capita vehicle travel may well have peaked, meaning a slower rate of traffic growth in the future. This is a good thing, as it means we can hopefully get away from an endless game of adding capacity to the road system only to see it fill up over and over again, hoping that perhaps this one last time the extra lane might solve congestion for good (like a drug addict wanting just one last hit?).
Of course, in the real world (rather than the fantasy world of Ministry of Transport policy analysts and NZTA traffic engineers) we understand that building more roads simply leads to inducing more traffic – meaning that more often than not you find yourself back to square one rather surprisingly quickly (ever noticed that the widest sections of Auckland’s motorway network often also seem to be the most congested?). This is well illustrated in the diagram below: Now it’s probably a bit unfair to say that there’s no benefit from allowing more vehicles to travel at the time they want to travel (as induced demand provides for) even if it means the road is still congested. But what Littman’s research shows is that there are diminishing returns when it comes to the value added – in that a lot of the people “induced” to using the road at peak times wouldn’t probably be quite willing to travel at other times, or via other modes, to avoid the peak congestion. The article goes on in quite a lot of detail about how we might better focus on reducing the impact of congestion – through building public transport, pricing roads and undertaking smarter land-use policies. There’s enough detail in those to probably fill a future post, but there’s one last graph that certainly caught my attention, because it looks at the wide variety of different costs – related to travel – that individual people face: What this graph shows really cleverly is that, in the broader scheme of everything, traffic congestion doesn’t really cost each of us that much money. Sure, it’s an annoyance, but then so is losing $2,000 a year in depreciation on our vehicles, having a cost to society of almost $2,000 a year from crash damages, paying (through higher rent, prices or lower salaries) parking subsidies and so forth. Yet for some reason our transport policy seems to be utterly obsessed with minmising the cost to us of what’s really quite a minor matter – only the sixth most important issue in terms of cost magnitude.
So automatic, so deep is the group-think at the MoT and NZTA, not to mention their close buddies in the road lobbies like the Road Users Forum and the AA, that the only possible answer to all questions of movement is to expand the road space, that these institutions are spending uncritically on projects with ever decreasing returns on the investment. Of course the pressure from their political masters is currently very great too and it all adds up to a deeply unsophisticated and wasteful approach to infrastructure investment and a less efficient and poorer city.
Of course, for some road users (freight movement and business travel comes to mind) congestion and unreliability have a much greater impact. But there really is something incredibly stupid and naive about over building one system that forces everyone, no matter how reluctant, into a car and in the way of these vital road users. Under this ideology it’s almost like the MoT and NZTA are really in the congestion business. Where is the analysis that shows that getting lower value trips onto public transport through investment in providing quality services wouldn’t be more cost effective than trying to squeeze ever more traffic onto already clogged roads? Especially because, as this study shows, congestion isn’t even the biggest burden of auto-dependency.