Many times in the last few years we have highlighted a ‘flat-lining’ or at least slowing of growth in car travel across New Zealand. The same trends have been seen in many overseas cities and countries – with the slowing in the UK dating back at least 20 years now. Yet for some bizarre reason this change hasn’t filtered through to those making projections about future traffic growth. In the UK we have seen projection after projection forecasting significant growth – even though consistently it doesn’t happen.
The same process has happened in Washington state, where the Department of Transportation has ignored the flat-lining of traffic growth and continued to forecast significant increases – despite all evidence suggesting they need to change:
Lance Wiggs has picked up on a recent report released by Treasury that looks into the evidence behind the key elements of the transport sector. Towards the end of the report Treasury analyses some projections of future transport demand prepared by NZTA and NZIER. Let’s let Lance pick up the story here:
This line records use of a certain item by New Zealand population since 2000. Where do you think it will be in say 20 years time?
The statistic went up, and then down, and so the best estimate to me would be a flat or downward trend. But rather strangely the authors of this chart determined that all of their estimates would be up, and that the lowest change would be a substantial increase. Here it is, with my added red line eyeball trend:
The chart, of course, is estimated vehicle use in New Zealand, expressed in millions of kilometres travelled. It’s sourced from the “ National Long-Term Land Transport Demand Model, NZIER and NZTA (2013)”, and that’s a critical model as it feeds into all sorts of cost-benefit analysis and policy for transport in New Zealand.
The data is sourced from this report, which appears to make the same mistakes as transport modelling projections in the UK and Washington state have done for the past 20 years – by refusing to believe that anything ever changes about how people travel. Even though evidence to the contrary is absolutely everywhere. Similar bizarre conclusions are made about future levels of public transport use. Back to Lance:
The bias towards cars is also reflected in this chart of forecast public transport statistics – which doesn’t pass the giggle test either. Witness the trend and the projections below (the red is my version of the trend-line):
So for some unfathomable reason the growth in the use of public transport is forecast to immediately and dramatically fall, while the growth in the use of cars will immediately and dramatically rise. It’s ludicrous.
What’s interesting is that a footnote in the Treasury paper notes that these projected trends are completely at odds with what has been happening in recent years. It says:
We note that, although the NZIER / NZTA model predicts a gradual decline in the future, the public transport share of passenger kilometres has shown a steady growth trend over the past decade. This may merit further monitoring and consideration as time progresses.
It seems that at least the public transport projections are a little bit too insane for even Treasury to believe.
In any other area of government activity or a business if the computer models were projecting the complete opposite of what’s happening, what’s been happening for quite some time and what’s happening in cities and countries all over the world, we’d chuck the models out and start again. Yet for some reason we keep believing these illogical outputs and use them to determine where and how to spend billions of dollars of public money. It’s quite disgraceful really.