How (In)accurate Are Demand Forecasts in Public Works Projects? The Case of Transportation

This article presents results from the first statistically significant study of traffic forecasts in transportation infrastructure projects. The sample used is the largest of its kind, covering 210 projects in 14 nations worth US$59 billion. The study shows with very high statistical significance that forecasters generally do a poor job of estimating the demand for transportation infrastructure projects. The result is substantial downside financial and economic risks. Such risks are typically ignored or downplayed by planners and decision makers, to the detriment of social and economic welfare. For nine out of ten rail projects passenger forecasts are overestimated; average overestimation is 106 percent. This results in large benefit shortfalls for rail projects. For half of all road projects the difference between actual and forecasted traffic is more than plus/minus 20 percent. Forecasts have not become more accurate over the 30-year period studied. If techniques and skills for arriving at accurate demand forecasts have improved over time, as often claimed by forecasters, this does not show in the data. The causes of inaccuracy in forecasts are different for rail and road projects, with political causes playing a larger role for rail than for road. The cure is transparency, accountability, and new forecasting methods. The challenge is to change the governance structures for forecasting and project development. The article shows how planners may help achieve this.Comment: arXiv admin note: text overlap with arXiv:1302.2544, arXiv:1303.6571, arXiv:1302.364

Store transportprojekter: - Før-og-efter studier af trafik og økonomi

Kun lidt forskning er blevet lavet omkring før- og efter studier af trafik og økonomi i store transport projekter. De få undersøgelser der er lavet peger i samme retning, nemlig at prognoserne for anlægsomkostningerne er undervurderet og trafikprognoserne er overvurderet. Resultaterne af en undersøgelse af fem danske bro- og tunnelprojekter blev sammenholdt med resultaterne fra udenlandske undersøgelser. Ud af 41 projekter var anlægsomkostningerne i trefjerdedele af tilfældene undervurderet og oftest, i en tredjedel af projekterne, var anlægsomkostningerne mellem 50% og 100% undervurderet. Prognosticeret og faktiske trafik blev undersøgt for 22 projekter og i ni ud af ti tilfælde var trafikprognoserne overvurderet. Hyppigst, i knap halvdelen af projekterne, var trafikprognoserne mellem 20% og 60% overvurderet. En konsekvens af for optimistiske prognoser er at beslutningstagere og befolkningen bliver vildledt og at de forkerte beslutninger træffes. &nbsp

Early Stage Alpha-Synuclein Amyloid Fibrils are Reservoirs of Membrane-Binding Species

Abstract The presence of αSN fibrils indisputably associates with the development of synucleinopathies. However, while certain fibril morphologies have been linked to downstream pathological phenotypes, others appear less harmful, leading to the concept of fibril strains, originally described in relation to prion disease. Indeed, the presence of fibrils does not associate directly with neurotoxicity. Rather, it has been suggested that the toxic compounds are soluble amyloidogenic oligomers, potentially co-existing with fibrils. Here, combining synchrotron radiation circular dichroism, transmission electron microscopy and binding assays on native plasma membrane sheets, we reveal distinct biological and biophysical differences between initial and matured fibrils, transformed within the timespan of few days. Immature fibrils are reservoirs of membrane-binding species, which in response to even gentle experimental changes release into solution in a reversible manner. In contrast, mature fibrils, albeit macroscopically indistinguishable from their less mature counterparts, are structurally robust, shielding the solution from the membrane active soluble species. We thus show that particular biological activity resides transiently with the fibrillating sample, distinct for one, but not the other, spontaneously formed fibril polymorph. These results shed new light on the principles of fibril polymorphism with consequent impact on future design of assays and therapeutic development

The restructuring and privatisation of British Rail: Was it really that bad?

This paper uses a social cost-benefit analysis (SCBA) framework to assess whether rail privatisation in Britain has produced savings in operating costs. The paper shows that major efficiencies have been achieved, consumers have benefited through lower prices, whilst the increased government subsidy has been largely recouped through privatisation proceeds. We also find that output quality is no lower (and is probably better) than under the counterfactual scenario of public ownership (pre-Hatfield). The achievement of further savings is key to delivering improved rail services in the future. This paper finds that a privatised structure, where shareholders demand a return on their investment, has led to significant improvements in operating efficiency - it remains to be seen whether the new regime, with a not-for-profit infrastructure owner, will deliver the same efficiency improvements