The Impacts of Using a Safety Compliance Standard in Highway Design

Dr. Ossenbruggen introduces an algorithmic method to objectively test and evaluate safety in the highway design process

A Method of Identifying Hazardous Highway Locations Using the Principle of Individual Lifetime Risk

Dr. Ossenbruggen presents a scientific framework for identifying hazardous highway locations that may be more easily understood by non-scientists and has potential for comparing highway with other risks to health

Potential Failure of A Decayed Tree Under Wind Loading

Trees with decayed wood that are subject to moderate winds often collapse and cause property damage or injury and death to people. The purpose of this paper is to describe a decision-making aid to help identify a tree that may fail in the forest or be a potential hazard in the city. A tree may fail when the probability of radial shear cracks developing for a given wind load is sufficiently high.Mathematical models are used to estimate the constant wind force on trees and to evaluate the cracking and collapse mechanisms under this loading. The physical dimensions are used to determine the wind force or drag on the tree, and the amount of decay in the tree is used to determine its ability to resist this load. Owing to uncertainties associated with accurately measuring and modeling a decayed tree, estimating the wind load, and specifying the wood strength of a tree species, reliability analysis is used to assess the potential risk of failure. Coupling this information with meteorological data for the largest wind speed value expected at the tree site and the topography of the tree site completes the analysis of potential failure. Case studies of balsam fir trees with the same exterior diameters but with different dimensions of decay columns, tree weights, tree heights, and wind speed conditions are analyzed and compared

Fundamental principles of systems analysis and decision-making

xiv, 412 hal; 25 c

Effect of time-of-day and day-of-the-week on congestion duration and breakdown: A case study at a bottleneck in Salem, NH

This work uses regression models to analyze two characteristics of recurrent congestion: breakdown, the transition from freely flowing conditions to a congested state, and duration, the time between the onset and clearance of recurrent congestion. First, we apply a binary logistic regression model where a continuous measurement for traffic flow and a dichotomous categorical variable for time-of-day (AM- or PM-rush hours) is used to predict the probability of breakdown. Second, we apply an ordinary least squares regression model where categorical variables for time-of-day (AM- or PM-rush hours) and day-of-the-week (Monday–Thursday or Friday) are used to predict recurrent congestion duration. Models are fitted to data collected from a bottleneck on I-93 in Salem, NH, over a period of 9 months. Results from the breakdown model, predict probabilities of recurrent congestion, are consistent with observed traffic and illustrate an upshift in breakdown probabilities between the AM- and PM-rush periods. Results from the regression model for congestion duration reveal the presences of significant interaction between time-of-day and day-of-the-week. Thus, the effect of time-of-day on congestion duration depends on the day-of-the-week. This work provides a simplification of recurrent congestion and recovery, very noisy processes. Simplification, conveying complex relationships with simple statistical summaries-facts, is a practical and powerful tool for traffic administrators to use in the decision-making process