Browsing by Author "Evans, Robert"

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    Assessing the Impacts of Pavement Surface Condition on the Performance of Signalized Intersections
    Hussein, Nasreen A.; Hassan, Rayya A.; Evans, Robert (2015-06-04)
    Signalized intersections are one of the most dangerous places on the road network as they carry a very high crash risk. This may be exacerbated by inadequate pavement surface condition. The main objective of this study was to assess the effect of pavement surface condition (in terms of skid resistance, roughness and rutting) at intersections and approaches on users' safety. In particular, this paper studied the change in crash frequency for numerous signalized intersections before and after surface treatment. Around one hundred sites were selected based on historical crash incident data and pavement maintenance records. Pavement condition data was extracted for these sites one year before and one year after surface treatment. For all sites, a minimum of three years crash data was used before and after treatment. Reported in this paper are the findings of an assessment of the changes in crash rates, types and severity due to surface treatment. Overall, assessment of the effect of surface treatment revealed a statistically significant reduction in crash rates of 0.49 at 95% confidence level with a p value of 0.006, based on a paired t-test. Negative binomial regression analysis was performed using pavement condition data, traffic volume and speed limit as the predictor variables of crash frequency. The results showed that both traffic volume and the interaction between traffic volume and skid resistance were significant contributors to the crash occurrence. However, for after treatment no independent variable had a significant contribution to the crash occurrence.
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    Characterization of Atypical Hemolytic Ornithobacterium rhinotracheale Isolates and Comparison with the Normal Non-Hemolytic Phenotype
    Walters, Jessica Nicole (Virginia Tech, 2014-10-24)
    Ornithobacterium rhinotracheale (ORT) is a Gram-negative bacterium that causes respiratory disease in poultry characterized by rhinitis, tracheitis, and pneumonia with mortality averaging 2-3%. In the Shenandoah Valley of Virginia, the seroprevalence for ORT among turkey flocks as determined by enzyme-linked immunosorbent assay (ELISA) was found to be 70.9% (n=175). Additionally, the seroprevalence for hemorrhagic enteritis virus (vaccine induced), Bordetella avium, and paramyxovirus-1 was 100%, 74.8%, and 6.3% respectively. No significant interactions were detected. The type strain of ORT is characteristically non-hemolytic at least for 96 hours at 37°C on Columbia Blood Agar. In recent years, atypical isolates that rapidly produce hemolysis have been isolated with increasing frequency. A variety of in vitro tests were used to determine differences between representative isolates of the hemolytic (H) and non-hemolytic (NH) phenotypes. Findings suggest that the H isolate contains a 4 kb plasmid similar to that found in Reimerella anatipestifer. No plasmid was found in the NH isolate. Differences in growth characteristics and resistance to tetracyclines were also noted. No differences in proteins, biochemical characteristics or 16S rRNA sequences were found, the latter serving as confirmation that the isolates were both ORT. Embryo inoculation was used to assess virulence. No significant differences were observed and most embryos survived through to the day of hatch (pip) despite the fact that ORT could be re-isolated. In turkey poults however, the H phenotype did appear less virulent. A significant depression in weight gain was noted for birds inoculated intratracheally with the NH isolate at 7 days post-inoculation (dpi). NH inoculates also had significantly higher antibody levels on ELISA at 14 and 21 dpi and histopathological lesion scores for lung at 7, 14, and 21 dpi. The NH isolate could be re-isolated from NH-inoculated poults through 21 dpi; whereas the H isolate could only be re-isolated through 14 dpi. In conclusion, there are numerous differences between the NH and H isolates found in the field with the H isolate appearing less virulent and as such, making it a potential vaccine candidate. The phenotypic difference appears to correlate with this, but may not suffice to explain it.
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    Effect of Traffic and Environmental Factors on Roughness Progression Rate of Sealed Low Volume Arterials
    Alaswadko, Nahla; Hassan, Rayya A.; Evans, Robert (2015-06-04)
    A high proportion of the rural arterial network in Victoria /Australia are low volume roads built of sealed granular pavements, which are important routes for freight movement between rural centres. Investigation into rehabilitation of these arterials is triggered when roughness reaches a certain threshold level. To assist road agencies in their long term planning, a project has been initiated to develop absolute deterministic deterioration models for these roads. A representative sample network of low volume arterial roads has been selected and all relevant data including pavement condition are collected. The network covers a representative range of traffic loading, subgrade reactivity level and environmental factors. For each highway section, raw longitudinal profile data from at least four years was used to determine roughness progression over time. All profile data was aligned and then cleaned and filtered to ensure that the same length of road profile was compared over time. To remove the influence of maintenance activities, only sections with positive progression was included. Multiple linear regression analysis was used to develop models for these sections to predict pavement roughness over time as a function of a number of contributing variables. The output of the analyses was used to evaluate the significance and contribution of the different factors including traffic and environmental conditions. This paper provides a description of data preparation and analysis. It was observed that higher traffic loading and soil reactivity, poor drainage and climates with high seasonal variation increase roughness progression rate.
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    Identifying Waveband Roughness in Highway Pavements Using Power Spectral Density Analysis
    Evans, Robert; Arulrajah, Arul (2015-06-04)
    The international roughness index and the ride number are the most common road profile indices used throughout the world today, which are both based on the response of a simulated passenger car travelling at 80 km per hour. Unfortunately, both of these indices only provide a summary of the road condition (according to a passenger vehicle) and do not provide any information about the likely cause of pavement deterioration or provide any insight into the most effective maintenance strategy to employ to remedy the pavement. As past studies have postulated that there is link between type of waveband roughness present in a pavement and cause of deterioration, a series of new waveband profile indices using Power Spectral Density (PSD) analysis have been developed to quantify the amount of waveband roughness present in a pavement. Moreover, these profile indices have been developed into a series of easy to use templates that can identify pavement sections containing abnormally high concentrations of waveband roughness (particularly long wavelength roughness). By identifying the dominant roughness waveband that contributes most towards pavement deterioration, better future maintenance decisions should naturally result. Although these waveband identification templates have been based on a set of rural highways in north-west Victoria, Australia, the methodology could be applied to other pavement sets throughout the world.