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

Novel Exploration Techniques (NETs) for Malaria Policy Interventions

The task of decision-making under uncertainty is daunting, especially for problems which have significant complexity. Healthcare policy makers across the globe are facing problems under challenging constraints, with limited tools to help them make data driven decisions. In this work we frame the process of finding an optimal malaria policy as a stochastic multi-armed bandit problem, and implement three agent based strategies to explore the policy space. We apply a Gaussian Process regression to the findings of each agent, both for comparison and to account for stochastic results from simulating the spread of malaria in a fixed population. The generated policy spaces are compared with published results to give a direct reference with human expert decisions for the same simulated population. Our novel approach provides a powerful resource for policy makers, and a platform which can be readily extended to capture future more nuanced policy spaces.Comment: Under-revie

Seismic characteristics of earthquakes along the offshore extension of the western transverse ranges, California

The short- and long-period body waves of five moderate (M_L 5 to 6) earthquakes that took place in the nearshore region of southcentral California between 1969 and 1981 are modeled to obtain the source parameters. Both regional Pnl waveforms and teleseismic P waveforms are used in this analysis. Four of the events are thrust earthquakes with strikes that rotate southwestward as the epicenters move southward; the fifth is a strike-slip event occurring on a fault subparallel to the San Andreas fault. The focal mechanisms for all five events are consistent with known faults in the source localities and suggest that the regional stress field is compressional in a north-south direction. At least three events have complex source time histories, suggesting that complex sources are common even for events of this size. The most exotic event started with a low stress drop subevent, ruptured bilaterally, and concluded with strong asperity ruptures at each end. Since Pnl waveforms for thrust events are particularly sensitive to crustal thickness, regionalized crustal models were developed. The crustal thickness appears to increase southward but may be a function of the distance of the event from shore rather than of latitude. Basin and range paths yield the thinnest crustal models, while paths crossing the Colorado Plateau and Rockies yield the thickest. We also examined amplitude variations with station and path. In general, the amplitudes seem to be controlled by the station site rather than the path

Rate of Strength Decrease of Fiber-Reinforced Ceramic-Matrix Composites during Fatigue

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65181/1/j.1151-2916.2000.tb01412.x.pd