No description available.

No description available.

No description available.

Changing speed limit leads to proportional changes in average speeds which may affect the number of traffic accident occurrences. It is however critical and challenging to evaluate the impact of a speed limit alteration on the number and severity of accidents due primarily to the unavailability of adequate data and the inherent limitations of existing approaches. Although speed is regarded as one of the main contributory factors in traffic accident occurrences, research findings are inconsistent. Independent of the robustness of their statistical approaches, accident frequency models typically use accident grouping concepts based on spatial criteria (e.g. accident counts by link termed as a link-based approach). In the link-based approach, the variability of accidents is explained by highly aggregated average measures of explanatory variables that may be inappropriate, especially for time-varying variables such as speed and volume. This thesis re-examines accident-speed relationships by developing a new accident data aggregation method that enables improved representation of the road conditions just before accident occurrences in order to evaluate the impact of a potential speed limit increase on the UK motorways (e.g. from 70 mph to 80 mph). In this work, accidents are aggregated according to the similarity of their pre-accident traffic and geometric conditions, forming an alternative accident count dataset termed as the condition-based approach. Accident-speed relationships are separately developed and compared for both approaches (i.e. link-based and condition-based) by employing the reported annual accidents that occurred on the Strategic Road Network of England in 2012 along with traffic and geometric variables. Accident locations were refined using a fuzzy-logic-based algorithm designed for the study area with 98.9% estimated accuracy. The datasets were modelled by injury severity (i.e. fatal and serious or slight) and by number of vehicles involved (i.e. single-vehicle and multiple-vehicle) using the multivariate Poisson lognormal regression, with spatial effects for the link-based model under a full Bayesian inference method. The results of the condition-based models imply that single-vehicle accidents of all severities and multiple-vehicle accidents with fatal or serious injuries increase at higher speed conditions, particularly when these are combined with lower volumes. Multiple-vehicle slight injury accidents were not found to be related with higher speeds, but instead with congested traffic. The outcomes of the link-based model were almost the opposite; suggesting that the speed-accident relationship is negative. The differences between the results reveal that data aggregation may be crucial, yet so far overlooked in the methodological aspect of accident data analyses. By employing the speed elasticity of motorway accidents that was derived from the calibrated condition-based models it has been found that a 10 mph increase in UK motorway speed limit (i.e. from 70 mph to 80 mph) would result in a 6-12% increase in fatal and serious injury accidents and 1-3% increase in slight injury accidents.

Thèse d'exercice : Médecine : Nancy 1 : 2009. / Titre provenant de l'écran-titre.

The effectiveness of speed limits has been the subject of considerable debate over the years. In most cases in the past, speed limits have been changed because of a single factor (e. g. improving the safety of road traffic or saving energy). In this thesis an attempt has been made to evaluate the consequences of changing a speed limit using cost-benefit analysis which formed the principle objective of this study. The scope was confined to motorways and similar high-quality roads operating under free-flow traffic conditions where speed limits were believed to be most effective. To achieve the main goal, the effect of the speed limit on the mean speed of traffic was investigated which was the second objective of the study. The third objective was to find the effect of the speed of traffic, and especially the mean speed of traffic, on the frequency and severity of personal injury accidents. There was a need to investigate these two relationships as the literature was not consistent on these relationships. A hypothesis was proposed to achieve the second objective. This was tested by defining criteria that had to be met for each of the data collection sites and measuring the speed of vehicles. There were II sites in Tyne & Wear, England and 14 sites in the State of Bahrain. A statistical analysis was applied to the data collected. It was found, from both sets of data, that speed limits had a positive effect on the mean speed and the eighty-fifth percentile speed of traffic. Linear and non-linear (multiplicative) models were developed for each set of data. In addition to the speed limit, the trip length and the length of the section were shown to affect significantly the mean speed of traffic. The amount of change in the mean speed of traffic varied between the models tested but, generally, for every 4 to 5 km/h change in the speed limit the mean speed of traffic changed by, about, I km/h. In a similar way, a hypothesis was proposed to pursue the third objective. Criteria were established for the selection of suitable data collection sites and for the types of accidents. 9 sites were selected in Tyne & Wear and 10 sites in the State of Bahrain. Data was drawn from a5 year set of accident records in Tyne and Wear and a four year set in the State of Bahrain. A statistical analysis was applied to the data. The set of data from Tyne & Wear revealed no significant relationship between the mean speed of traffic and the frequency of accidents but the speed differentials affected the frequency of the personal injury accidents. The data from Bahrain showed that both the mean speed of traffic and the speed differentials of vehicles affected the frequency of the personal injury accidents. No significant relationships were found between the speed of vehicles and the severity of the personal injury accidents. The principle objective of the study was achieved by applying cost-benefit analysis to the consequences of changing the speed limit for a hypothetical typical section of road. The components of cost were the cost of travel-time, the vehicle operating cost, and the cost of accidents. No monetary values were assigned to the environmental effects so it was not possible to include them in the cost-benefit analysis but they were acknowledged. Any changes in air pollution and noise annoyance due to a change in the mean speed of traffic following a change in a speed limit were likely to be small and were not considered in the study. The significance of the uncertainty in the frequency and severity of personal injury accidents in relation to the mean speed of traffic was studied using 'break-even analysis'. Generally, it was believed that lowering the speed limit on motorways and similar high-quality roads would produce negative benefits, even if the frequency and severity of personal injury accidents decreasedw ithin expectedr anges. Increasing the speed limits would produce positive economic benefits but the conclusion was less firm than the previous case. Sensitivity analysis was applied to the variables used in the cost-benefit analysis. It was found that the net benefits were most sensitive to the estimation of the effect of the speed limits on the mean speed of traffic, the initial mean speed of traffic in the base year of the assessment, the travel-time cost, the changes in the frequency of the personal injury accidents, and changes in the number of fatal injury casualties per average personal injury accident as the speed limit varied (i. e. in descending order for most speed limits). The ranking of these variables differed as the speed limit was changed.

In order to prevent accidents we need to understand them, this is achieved through effective accident investigation. Accident investigation is a complex process of gathering and evaluating information to determine factors that may have implications on the final event. One of the fundamental aspects in the investigation process is to capture geospatial data of the incident, to document the scene in its current condition, providing the investigation team with a record for future reference. The production of plans have conventionally remained the same, with a surveyor tasked to illustrate a 3D scene with 2D representations. Recent developments in instrumentation have provided the geospatial industry with the means to capture vast amounts of 3D data directly using laser scanning. In addition, there have been considerable advancements in software applications which can be used to process the surveyed datasets. This research evaluates the use of the latest technology in respect of accident investigation applying the methodology to fire related incidents, industrial accidents and mining incidents. This is achieved by using a number of case studies that have been undertaken throughout the timeline of the project and whilst working with industry professionals in the field.

No description available.

Diss. (sammanfattning) Stockholm : Karol. inst., 2001. / Härtill 6 uppsatser.

Thesis (M.P.H.)--Georgia State University, 2008. / Title from file title page. Karen Gieseker, committee chair; Ike S. Okosun, Victoria Espitia-Hardeman, committee members. Electronic text (69 p. : col. ill., col. map) : digital, PDF file. Description based on contents viewed Sept. 29, 2008. Includes bibliographical references (p. 61-66).