An evaluation of the implications of imposing speed limits on major roads

PhD ThesisThe 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.University of Bahrai

Patterns of Reading Errors among Emirati Second Grade Students

The impact of morphological awareness on reading proficiency has been neglected and there has been much focus on researching the impact of phonological awareness on reading skills. The aim of this study was to examine reading errors among second-grade Emeriti students by mapping a threefold paradigm (i.e., difficulty level, lexical category, and reading error patterns). The study sample included 168 Emirati second grade students (87 males and 81 females). One hundred forty four words were randomly selected from the Arabic reading curriculum. Those words were classified into lexical categories as nouns (45%), verbs (34%), adjectives and adverbs (10%), and functional words (i.e., prepositions and conjunctions; 11%). Those words were classified into three levels of linguistic difficulty (i.e., easy, difficult, and very difficult) according to their morphological complexity. The results revealed that reading difficulties may be the result of a threefold interrelated paradigm: the difficulty level of the words (i.e., morphological complexity), the lexical category (i.e., nouns, verbs, adjective and adverbs, and prepositions and conjunctions), and the pattern of the reading error (e.g., omission of a letter or a syllable and reading the geminated letter as ingeminated). The results also indicated that identifying this paradigm in each student can be useful in early detection of reading difficulty and thus, may assist in constructing appropriate remedial programs

Comorbidities Associated With Attention-Deficit/Hyperactivity Disorder in Children and Adolescents at a Tertiary Care Setting

Studies have revealed high rates of neurodevelopmental and psychiatric comorbid conditions among individuals diagnosed with attention-deficit/hyperactivity disorder (ADHD). However, research on this topic in the Arab world has been limited. This study evaluates the medical, neurodevelopmental, and psychiatric comorbidities in children and adolescents diagnosed with ADHD in Dubai, United Arab Emirates (UAE). A total of 428 pediatric patients diagnosed with ADHD were included. Children and adolescents with ADHD had high rates of comorbid disorders. Twenty comorbid conditions were identified. More than 3 quarters of the study sample had at least 1 comorbid disorder. The most common comorbidity among children was autism spectrum disorder, and among adolescents was anxiety disorders. Comprehensive assessments are highly warranted to identify and manage associated comorbid conditions. Further research is needed in exploring the biopsychosocial factors contributing to the elevated rate of comorbidity in children and adolescents with ADHD

Comparative Study of Two Semi-automated Forensic DNA Extraction Methods

Automation in forensic DNA analysis is crucial for analysts to reduce time, improve results, and decrease risk of contamination. With the variety of commercially available automated DNA extraction systems, comes the need for end-users to be informed of what they provide and what they might lack. Thus, this study aimed to evaluate the efficiency of two semi-automated DNA extraction systems used for forensic DNA analysis: Automate Express™ and Hamilton Microlab STAR™ system, for four parameters; reproducibility, stability, sensitivity and contamination. Overall, the results indicated that both semi-automated systems performed similarly in providing robust and reproducible DNA results while maintaining good capability to overcome PCR inhibition with low risk of contamination. The two semi-automated systems showed higher DNA recovery than organic extraction using phenol-chloroform by 22% for semen and 7% for blood samples. In addition, three sample types, blood, saliva, semen were tested to compare the two systems (total samples n=100). Overall, the data showed the average DNA recovery for Hamilton was higher than the DNA recovery by Automate Express™ for the blood and semen sample types indicating better performance of the Hamilton Microlab STAR™ in terms of recovery and sensitivity level

Performance of Different Cotton and Nylon Swabs on DNA Recovery and Storage

Touch DNA samples are routine yet challenging pieces of evidence that provide investigators with information that helps them solve crimes. However, this type of evidence can be easily lost if the correct collection method is not used. This problem could be overcome with an optimal method of collection that increases the amount of touch DNA collected from different types of surfaces. Better-quality touch DNA can increase the chances of getting a full genetic profile. This study was divided into two parts which aimed to assess whether the type of swab used on different surfaces will significantly increase DNA recovery, concentrations, and the DNA preservation during three different timeframes (24h, 1 month and 3 months). Two different cotton swabs and Nylon swabs were used to lift touch DNA on three different surfaces (glass, plastic and wood) to identify the most suitable method of collection across all three surfaces. A total of 72 samples were lifted (3 replicates from each swab on 3 different surfaces) from two different participants (Male and Female) which were left to dry for 14 days in room temperature prior to DNA extraction. DNA preservation of the swabs was observed while using three dilutions of blood sample which was prepared from one of the volunteers (1:1 – 1:10 – 1:20) where 10 uL of each dilution was pipetted onto the four types of swabs in three replicates (n=36) to observe the preservation over three different timeframes 24h storage, 1 Month and 3 Months with a total of 108 samples. The COPAN CLASSIQSwabsTM Dry swab showed an overall average result during the storage periods of 24h with (1:1) dilution by (2.694ng/μL), (1:10) dilution with (0.548ng/μL) and (1:20) dilution with (0.143ng/μL). Results for the period of 1 Month also showed an average of (1:1) dilution with (2.825ng/μL), (1:10) dilution with (0.361ng/μL) and (1:20) dilution with (0.156ng/μL). These findings can be helpful for laboratories and crime scene investigators to optimize DNA sample collection and preservation based on their workflow

Use of speed profile as surrogate measure: Effect of traffic calming devices on crosstown road safety performance

Urban road safety management is usually characterized by the lack of sufficient, good quality crash data and low budgets to obtain it even though many traffic accidents occur there. For example, 54 percent of road crashes in Spain take place in urban areas, and 10 percent of urban fatal crashes occur on crosstown roads, which are rural roads that traverse small communities. Traffic calming measures (TCMs) are often implemented on these parts of rural roads that traverse small communities in order to reduce both the frequency and severity of crashes by lowering speeds, but evaluation of their effectiveness has been limited. The objective of this study was to develop a methodology using continuous speed profiles to evaluate the safety effectiveness of TCMs on crosstown roads as part of an integrated system in the absence of historical data. Given the strong relationship between speed and crash experience, safety performance can be related to speed. Consequently, speed can be used indirectly as a surrogate safety measure in the absence of crash and speed data. Two indexes were defined in this study as surrogate safety measures based on the continuous speed profile: Ra and Ea. Ra represents the absolute accumulated speed variations relative to the average speed and is inversely related to accumulated speed uniformity; and Ea represents the accumulated speed variations above the speed limit and is directly related to accumulated speeding. Naturalistic data were collected using GPS trackers for 12 scenarios with different TCM spacings. Then, the indexes were applied to individual observed speed profiles (individual analysis) as well as the operating speed profile (global analysis). The values obtained from individual and global analysis were statistically different. Spacing lower than 110 m, which was found optimal from previous research, did not allow drivers to modify their speeds as the accumulated speed uniformity was quite similar regardless of the average operating speed; and, accumulated speeding was also minimized. Consequently, the scenarios where the TCMs were implemented according to the technical criteria presented a better design quality. On the other hand, age and gender differences did not seem to affect the average speeds or the accumulated speed uniformity and accumulated speeding.Moreno Chou, AT.; García García, A. (2013). Use of speed profile as surrogate measure: Effect of traffic calming devices on crosstown road safety performance. Accident Analysis and Prevention. 61:23-32. doi:10.1016/j.aap.2012.10.013S23326

Civic Nationalism and Language-in-Education Policies in the United Arab Emirates

A founding principle of the United Arab Emirates is the belief that tolerance promotes peace, while isolation encourages division and conflict. With more than 200 nationalities residing in the UAE, Emiratis constitute only 10% of the population, making them a minority in their own country. Despite the government promoting diversity and tolerance as the norm, such demographic imbalance come with a cost to the Arabic language, the national identity and culture, and the education system. This chapter addresses those concerns through a series of recent government initiatives. The author classifies neo-nationalist movements into different types, arguing that the one in the UAE largely fits within the civic type with its non-hostile, overall welcoming attitude toward foreigners. At the end of the chapter, she discusses the impact of neo-nationalism on education and calls for clearer policies that take into account language(s) as a right and as a resource

The influence of economic incentives linked to road safety indicators on accidents: The case of toll concessions in Spain

The goal of this paper is to evaluate whether the incentives incorporated in toll highway concession contracts in order to encourage private operators to adopt measures to reduce accidents are actually effective at improving safety. To this end, we implemented negative binomial regression models using information about highway characteristics and accident data from toll highway concessions in Spain from 2007 to 2009. Our results show that even though road safety is highly influenced by variables that are not managed by the contractor, such as the annual average daily traffic (AADT), the percentage of heavy vehicles on the highway, number of lanes, number of intersections and average speed; the implementation of these incentives has a positive influence on the reduction of accidents and injuries. Consequently, this measure seems to be an effective way of improving safety performance in road networks