Under-estimating the cost of major infrastructure projects and over-estimating the demand is so chronic that forecasters deserve some harsh medicine, according to Professor Bent Flyvbjerg from Oxford University’s Said Business School. He says “some forecasts are so grossly misrepresented that we need to consider not only firing the forecasters but suing them too – perhaps even having a few serve time”.
Australians have plenty of experience with underperforming infrastructure projects. For starters, just in transport alone, there’s Brisbane’s Clem 7 road tunnel, Sydney’s Lane Cove and Cross City tunnels, the Brisbane and Sydney airport trains, Melbourne’s Myki ticketing fiasco, and the 2,250 km Freightlink rail line connecting Adelaide and Darwin. And they’re just the ones we know about!
Professor Flyvbjerg says cost overruns in the order of 50% in real terms are common for major infrastructure projects and overruns above 100% are not uncommon. Writing in the Oxford Review of Economic Policy, he argues that demand and benefit forecasts that are wrong by 20–70% compared with the actual outcome are also common.
Transport projects are among the worst performers (see exhibit). Professor Flyvbjerg examined 258 transport projects in 20 nations over a 70 year time frame. He found the average cost overrun for rail projects is 44.7% measured in constant prices from the build decision. For bridges and tunnels, the equivalent figure is 33.8%, and for roads 20.4%. The difference in cost overrun between the three project types is statistically significant and the size of the standard deviations shown in the first exhibit demonstrate the high degree of uncertainty and risk associated with these sorts of projects.
He also found that nine out of 10 projects have cost overruns; they happen in all nations; they’ve been a constant over the last 70 years; and cost estimates have not improved over time.
And it’s not just under-estimation of costs. Errors in forecasts of travel demand for rail and road infrastructure are also endemic. He found that actual passenger traffic for rail projects is on average 51.4% lower than forecast traffic. He says:
This is equivalent to an average overestimate in rail passenger forecasts of no less than 105.6 per cent. The result is large benefit shortfalls for rail. For roads, actual vehicle traffic is on average 9.5 per cent higher than forecasted traffic. We see that rail passenger forecasts are biased, whereas this is less the case for road traffic forecasts.
He also found that nine out of ten rail projects over-estimate traffic; 84% are wrong by over ±20%; it occurs in all countries studied; and has not improved over time.
Thus the risk associated with rail projects in particular is extraordinary. They face both an average cost overrun of 44.7% and an average traffic shortfall of 51.4%. Read the rest of this entry »