There seems to be a global patterns among the Anglo-Saxon nations (and perhaps others). If you have more forecasting graphs like this for other places, please send them along via the Comments, and I will update this post.
Intercounty Connector Source: Image by Claire Jaffe
In other fields
Forecasts of Treasury Yields vs. reality.Delphi Energy ForecastJevons Coal ForecastEvolution of Brent Oil Forecasts: Source:Past Economic Outlook projections of euro area GDPDemographic Changes: Revisions to Japan’s Total Fertility Rate ForecastsWhy have the IEA’s projections of renewables growth been so much lower than the out-turn?“The energy world is undergoing massive transformation. Installations of renewable energy have skyrocketed around the world, exceeding most predictions from less than a decade ago. ” Source:State Revenue Forecasts are becoming increasingly wobbly. Source.Aurelija Augulyte (@auaurelija) 6/12/15, 03:44 writes: but hey don’t worry about Sweden. #Riksbank has it all under control. pic.twitter.com/NWdZfvUpaGGusher of Disappointment : Each month forecasters in the Wall Street Journal’s survey of economists have predicted that oil prices would climb. Each forecast is the average of responses to that month’s survey.Falling inflation. Forecasters have expected inflation, as measured by the Consumer-price index, to rise more quickly toward the Fed’s 2% larger. Each forecast is the average of responses of that month’s survey.Effective fed funds rate and forward rates implied by futures contracts
4 thoughts on “Extrapolations in Traffic vs. Reality”
Hi David, what is interesting here is the New Zealand Ministry of Transport’s belated recognition that the world is changing. The New Zealand graph you showed was put there to demonstrate just how wrong they had gotten traffic projections in the past not, as was past practice, simply to predict that a resumption of previous traffic growth is just around the corner. In fact, this is what they said about the figure you published: “Figure 2 illustrates how our traditional forecasting models have consistently overestimated demand.”
A quote from the future demand section of the Ministry of Transport website further illustrates this:
“The challenge we face, however, is there have recently been changes to the patterns of demand for personal travel. From 1980 to 2004 we saw annual increase in demand in the order of three percent per year. This highlighted the importance of tackling congestion and improving safety and gave us assurance revenue would grow to cover the costs of a growing network. From 2005 to 2013 total demand only grew by 0.25 percent per year. We now face an uncertain future. We cannot be certain demand will return to pre-2005 levels of growth nor can we be certain it will remain flat. This means we can no longer rely on traditional forecasting models alone to help us to decide how to invest. Figure 2 illustrates how our traditional forecasting models have consistently overestimated demand.”
The conclusions of the recent extensive work done in New Zealand on future demand are summarised as follows:
“When we think about creating a thriving New Zealand we should recognise we are trying to improve access not just mobility. There are three different ways we can achieve this: with good transport systems; with good spatial planning; or by improving digital access. We need to integrate our thinking across these three areas to achieve the optimal outcome.
To reduce the uncertainty we face we should seek to better understand the factors affecting the changing patterns of demand and refresh our demand models accordingly. We should look both at social trends and also speed in development, take-up and impact of new technologies.
To ensure resilience of the access system we develop for New Zealand we should seek to build in flexibility where we can. This will allow us to respond more quickly to changing patterns of demand and reduce the likelihood that we will make investments which will become unnecessary.
We need to recognise that the investment decisions we make will shape patterns of demand and not just respond to them. We should move away from the approach of seeking to simply predict future demand and then provide for it. We should instead debate the sort of access we want and decide how to invest to support the future.”
This official advice was presented by the Ministry of Transport in briefing papers to the new Minister of Transport (we had an election recently and as is the custom, the incoming government receives briefings from ministries on the big trends that ministers need to be aware of in their decision-making).
The GB Department for Transport argues that the traffic forecasting methodology they use is able to reproduce accurate backcasts of the ‘non-growth’ in traffic in the past decade, on the basis of ex post knowledge of fuel prices and other model inputs.
David Levinson, Transportist 
Hi David, what is interesting here is the New Zealand Ministry of Transport’s belated recognition that the world is changing. The New Zealand graph you showed was put there to demonstrate just how wrong they had gotten traffic projections in the past not, as was past practice, simply to predict that a resumption of previous traffic growth is just around the corner. In fact, this is what they said about the figure you published: “Figure 2 illustrates how our traditional forecasting models have consistently overestimated demand.”
A quote from the future demand section of the Ministry of Transport website further illustrates this:
“The challenge we face, however, is there have recently been changes to the patterns of demand for personal travel. From 1980 to 2004 we saw annual increase in demand in the order of three percent per year. This highlighted the importance of tackling congestion and improving safety and gave us assurance revenue would grow to cover the costs of a growing network. From 2005 to 2013 total demand only grew by 0.25 percent per year. We now face an uncertain future. We cannot be certain demand will return to pre-2005 levels of growth nor can we be certain it will remain flat. This means we can no longer rely on traditional forecasting models alone to help us to decide how to invest. Figure 2 illustrates how our traditional forecasting models have consistently overestimated demand.”
The conclusions of the recent extensive work done in New Zealand on future demand are summarised as follows:
“When we think about creating a thriving New Zealand we should recognise we are trying to improve access not just mobility. There are three different ways we can achieve this: with good transport systems; with good spatial planning; or by improving digital access. We need to integrate our thinking across these three areas to achieve the optimal outcome.
To reduce the uncertainty we face we should seek to better understand the factors affecting the changing patterns of demand and refresh our demand models accordingly. We should look both at social trends and also speed in development, take-up and impact of new technologies.
To ensure resilience of the access system we develop for New Zealand we should seek to build in flexibility where we can. This will allow us to respond more quickly to changing patterns of demand and reduce the likelihood that we will make investments which will become unnecessary.
We need to recognise that the investment decisions we make will shape patterns of demand and not just respond to them. We should move away from the approach of seeking to simply predict future demand and then provide for it. We should instead debate the sort of access we want and decide how to invest to support the future.”
This official advice was presented by the Ministry of Transport in briefing papers to the new Minister of Transport (we had an election recently and as is the custom, the incoming government receives briefings from ministries on the big trends that ministers need to be aware of in their decision-making).
It might be worth you looking at the really interesting future demand work that the NZ Ministry of Transport has done (and maybe even post on it) http://www.transport.govt.nz/assets/Uploads/Our-Work/Documents/fd-final-report.pdf
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Dear David —
The GB Department for Transport argues that the traffic forecasting methodology they use is able to reproduce accurate backcasts of the ‘non-growth’ in traffic in the past decade, on the basis of ex post knowledge of fuel prices and other model inputs.
I haven’t seen a published detailed evaluation showing the above, but the summary is in Figure 10 (p.16) of this report: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/260700/road-transport-forecasts-2013-extended-version.pdf
I’d be interested in hearing from you or others whether similar analysis has been undertaken in the rest of the Anglosphere–
–Scott
slevine@imperial.ac.uk
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Portugal:
Source: http://www.estradasdeportugal.pt/index.php/pt/informacoes/estudos/871-concessoes-rodoviarias-um-novo-paradigma-operacional (Portuguese)
Added to bad forecasting, the 2008 crisis and new tolls in highways that were meant to be toll-free when designed in the late 1990s.
Brazil so far is doing fine, let´s see.
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