SUMMARYPavement maintenance is essential for ensuring good riding quality and avoiding traffic congestion, air pollution, and accidents. Improving road safety is one of the most important objectives for pavement management systems. This study utilized the Tennessee Pavement Management System (PMS) and Accident History Database (AHD) to investigate the relationship between accident frequency and pavement distress variables. Focusing on four urban interstates with asphalt pavements, divided median types, and 55 mph speed limits, 21 Negative Binomial Regression models were developed for predicting various types of traffic accident frequencies based on different pavement condition variables, including rut depth (RD), International Roughness Index (IRI), and Present Serviceability Index (PSI). The modeling results indicated that the RD models did not perform well, except for predicting accidents at night and accidents under rain weather conditions; whereas, IRI and PSI were always significant prediction variables in all types of accident models. Comparing the models goodness-of-fit results, it was found that the PSI models had a better performance in crash frequency prediction than the RD models and IRI models. This study suggests that the PSI accident prediction models should be considered as a comprehensive approach to integrate the highway safety factors into the pavement management system.
The principal therapy for seromucinous otitis media is directed at reestablishing aeration of the middle ear cleft by the use of ventilating tubes, as first advocated by Armstrong (1954). This communication is an analysis of the results of management of seromucinous otitis media in matched pairs of ears by inserting a grommet in one ear and carrying out no operative intervention in the other ear. Acoustic impedance values: The mean readings of the middle ear pressures in the grommet and control ears were very similar in the 55 pairs and fell within the normal range quoted by Brooks
The long-term natural history of secretory otitis media and the changes induced in the middle ear following grommet insertion are of importance. We report the results 15 years following the unilateral insertion of a Shepard grommet and adenoidectomy for bilateral secretory otitis media. The results suggest that grommets do not protect against attic disease of late onset and induce atrophic scars which do not resolve. Grommets confer no long-term advantages to the hearing when used in the management of childhood secretory otitis media.
To address the dilemma between the need for truck transportation and the costs related to truck-involved crashes, the key is to identify the risk factors that significantly affect truck-involved crashes. The objective of this research is to estimate the effects of the characteristics of traffic, driver, geometry, and environment on severity of truck-involved crashes. Based on four crash severity categories (fatal/incapacitating, non-incapacitating, possible injury, and no injury/property damage only), a multinomial logit model is conducted to identify the risk factors. The investigation of risk ratios indicates that lower traffic volume with higher truck percentage is associated with more serious traffic crash with fatal/incapacitating injury while a non-standard geometric design is the main cause of non-incapacitating crashes. The influences of weather are significant for the possible-injury crashes while driver condition is the principal cause of no-injury/property-damage-only crashes. In addition, the statistical results demonstrate that the influence of the truck percentage is significant. One-unit change in the truck percentage will cause more than one times probability of being in an injury.
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