The correlation between gradients of descending roads and accident rates

The traffic accident rate on descending roads on mountainous highways is quite high. To study the effects of vertical gradient and length of road on traffic accidents on continuous descending roads, data from 1413 traffic accidents over an 85.43 km section of road were collected. By taking parameters such as the gradients in accident sites, and taking the average gradient in N km (N = 1, 2, 3, 4, 5) just prior to the accident sites as the profile parameter, scatter diagrams were drawn to explore the effects of the profile parameters on the distribution of traffic accidents. Analysis of the exponential regression and correlation analysis between accident rates and profile parameters was carried out as well. The research results show that the accident rate increases with average vertical gradient exponentially; the differences between accident rate and different profile parameters are significant; the accident rate has a good exponential relationship with average gradients when a section has a 2 km or 3 km slope just prior to the accident sites i.e. the accident rate at a specific section on a continuous descending road is related to the average gradient in 2–3 km descending sections just prior to the accident site. The findings indicate that a steep gradient alone is not the reason for an accident, but we also have to take into consideration the presence of a “continuous long” descent prior to it.     

Epidemiology of occupational accidents among Iranian insured workers

Work-related accidents are considered as a major health problem worldwide. The aim of present study was to determine the epidemiological pattern of occupational accidents among workers insured by the Iranian Social Security Organization (ISSO) between 2001 and 2005.Subjects consisted of all workers and drivers who had a work-related accident during 2001–2005 and were registered in the Iranian Social Security Organization (ISSO) database according to the inspection reports. An ordinal logistic regression model (proportional odds regression model) was used to assess the concurrent effects of independent variables on accident outcomes.Overall, 86,437 work-related accidents were investigated. The accidents were more frequent in metal workplaces and electrical industries, respectively. More than half of the accidents were due to incautious activities. Workers’ age (age at the time of accident) (OR = 0.99, CI: 0.989–0.994), gender (OR = 1.3, CI: 1.191–1.683), marital status (OR = 1.25, CI: 1.143–1.675) as well as accident setting (OR = 1.88, CI: 1.728–1.975) had significant effect on accident outcomes. Pattern of occupational injuries in Iran was consistent with the global pattern for accident outcomes.     

Large scale high pressure jet fires involving natural gas and natural gas/hydrogen mixtures

A series of six large scale high pressure jet fires were conducted using natural gas and natural gas/hydrogen mixtures. Three tests involved natural gas and three involved a mixture of natural gas and hydrogen containing approximately 24% by volume hydrogen. For each fuel, the three tests involved horizontal releases from 20, 35 and 50 mm diameter holes at a gauge pressure of approximately 60 bar. During the experiments, the flame length and the incident radiation field produced around the fire were measured. The fires also engulfed a 1 m diameter horizontal pipe placed across the flow direction and about halfway along the flame. This pipe was instrumented to measure the heat fluxes to the pipe. The data obtained is compared with previous data obtained for various hydrocarbons at large scale.     

Cultural and socio-demographic predictors of car accident involvement in Norway,Ghana, Tanzania and Uganda

The prevalence of road traffic accidents is increasing towards endemic proportions in developing countries. The present study investigated cultural and demographic predictors of car accident involvement in a developed country in Europe and three developing countries in Sub-Saharan Africa. The comparison was carried out with questionnaires among a randomly obtained representative sample of the Norwegian population (n = 247) as well as stratified samples in Accra and Cape-Coast in Ghana (n = 299), Dar-es-Salaam and Arusha areas in Tanzania (n = 599), and the central Kampala and the Mbarara district in Uganda (n = 415). Measurement instruments of culture as symbol exchange and destiny orientation were used to predict self-reported road traffic accident involvement by car among the respondents. Demographic characteristics, such as gender, age and education, were also included as predictors of car accidents. The results showed that male gender was the only significant predictor of accident involvement in Norway. Introverted and extroverted culture, destiny orientation and written culture were associated with accident involvement in the African countries. Male gender also predicted accidents in these countries. Non-technical injury preventive countermeasures in developing countries could focus on cultural practice and fatalistic beliefs. Countermeasures in both developed and developing countries should target male drivers.     

The self-defensive attribution hypothesis in the work environment: Co-workers’ perspectives

The study explored the possible influences of situational, personal and non-relevant perception on causality attributions and responsibility assignment in Ghana’s work environment. Ghanaian industrial workers (co-workers) who were witnesses to industrial accidents (n = 117) assigned causality for the mishap and their responses were compared. Analyses were based on the co-workers’ responses to open-ended questions. Three categories of co-workers were identified and labelled as situationally relevant (n = 34), personally relevant (n = 43) and non-relevant co-workers (n = 40). The results showed that co-workers (witnesses) who had some perception of situational and or personal relevance with the accident victims attributed less responsibility to the accident victims than did their counterparts who had no perception of relevance. This observation, like other motivated attributional distortions, seems to reflect a tendency towards self-protection from the three categories of co-workers. It confirms the self-defensive attribution hypothesis in causal attributions about accidents in the work environment.     

A study of pedestrian and bicyclist exposure to head injury in passenger car collisions based on accident data and simulations

The objective was to assess head injury risks and kinematics of adult pedestrians and bicyclists in primary impact to the passenger cars and secondary impact to the ground using real world accident data and computer reconstructions of the accidents. For this purpose, a subsample of 402 pedestrians and 940 bicyclists from the GIDAS database, Germany, was used for the statistical analysis, from which 22 pedestrian and 18 bicyclist accidents were further selected for reconstruction. PC-Crash was used to calculate impact conditions, such as vehicle impact velocity, vehicle kinematic sequence, and thrown distance. These conditions were employed to identify the initial conditions in reconstruction in MADYMO program. A comparable analysis was conducted based on the results from accident analysis and computer reconstructions for the impact configurations and the resulting injury patterns of pedestrians and bicyclists in view of head injury risks. Differences in HIC, head-relative impact velocity, linear acceleration, maximum angular velocity and acceleration, contact force, thrown distance, Wrap Around Distance (WAD), and head contact time were evaluated. Injury risk curves were generated by using a logistic regression model for vehicle impact velocity. The results indicate that bicyclists suffered less severe injuries compared with severity of pedestrian injuries. In the selected samples, the AIS 2+ and AIS 3+ head injury risks for pedestrians are 50% probability at impact speed of 38.87 km/h and 54.39 km/h respectively, while for bicyclists at 53.66 km/h and 58.89 km/h respectively. The findings of high injury risks suggested that in the area with high frequency car-pedestrian accidents, the vehicle speed limit should be 40 km/h, while in the area with high frequency car-cyclist accidents the vehicle speed limit should be 50 km/h.     

Educational status and organizational safety climate: Does educational attainment influence workers’ perceptions of workplace safety?

From a practical perspective, understanding the impact of education on perceptions of workplace safety would benefit management’s decisions regarding workers’ adaptability, general work effectiveness, accident frequency, implementation of safety management policies, and handling of education-related accident characteristics. The current study thus examined the relationship between educational attainment and (i) safety perception, (ii) job satisfaction, (iii) compliance with safety management policies, and (iv) accident frequency. Participants were Ghanaian industrial workers (N = 320) categorized into four educational groups based on their responses: basic education 50% (n = 159); secondary education, n = 98 (30%); vocational/professional education, 17% (n = 56); and university education, 3% (n = 7). Workplace safety perception was assessed with Hayes et al.’s 50-item Work Safety Scale (WSS): a scale that effectively captures the dimensions identified by safety experts to influence perceptions of workplace safety. Multivariate analysis (MANOVA) was used to test for differences of statistical significance. Posterior comparison with t-test consistently revealed significant differences between the two higher-educated cohorts and their lower-educated counterparts. The results indicated a positive association between education and safety perception. Higher-educated workers recorded the best perceptions on safety, indicated the highest level of job satisfaction, were the most compliant with safety procedures and recorded the lowest accident involvement rate.     

Effects of applied voltage on hydrogen production rate of a single reactor BML with Clostridium sp.

This study aimed to explore the influences of single-chamber systems with different applied voltage on bio-hydrogen (H₂) production. The reactor used was the bio-electrochemically assisted microbial reactor (BEAMR) membrane-less (BEAMR-membrane-less, BML). The microbial dark fermentative H₂ production method was adopted. After the hot screening process and the DNA sequencing, the domesticated dominant microflora was Clostridium sp. This study discussed the influences of the cases with (continuous and intermittent) and without applied voltage separately. The results showed that, the H₂ production rate of the case with intermittent applied voltage (117 mL/h g VSS) of 0.24 V was increased of 1.7 folds higher than the without applied voltage (69 mL/h g VSS) and 1.3 folds higher than the case with continuous applied voltage (88.2 mL/h g VSS) of 0.24 V. The produced H₂ concentration with intermittent applied voltage was 18.9% (18.6–19.1%) higher than the without applied voltage, while there was no significant difference with continuous applied voltage.     

Experimental study of the characteristics of solid fuel from fry-dried swine excreta

Swine excreta were dried by boiling via immersion in hot oil. In this method, moisture in the excreta is replaced with oil or evaporated by turbulent heat transfer in high-temperature oil. The dried excreta can be used in an incinerator like low-rank coal or solid fuel. Refined waste oil and B–C heavy oil were used for drying. Drying for 8 min at 150 °C reduced the water content of raw excreta from 78.90 wt.% to 1.56 wt.% (refined waste oil) or 1.62 wt.% (B–C heavy oil) and that of digested excreta from 79.58 wt.% to 3.40 wt.% (refined waste oil) or 3.48 wt.% (B–C heavy oil). The low heating values of the raw and digested excreta were 422 kJ/kg and ?2,713 kJ/kg, respectively, before drying and 27,842–28,169 kJ/kg and 14,394–14,905 kJ/kg, respectively, after drying. A heavy metal analysis did not detect Hg, Pb, Cd, As, and Cr in the dried excreta, but Al, Cu, and Zn, which occur in the feed formula, were detected. Thermogravimetric analysis before and after drying revealed that emission of volatiles and combustion of volatiles and fixed carbon occurred at temperatures of 250–500 °C when air was used as the transfer gas.     

Flammability of hydrocarbon and carbon dioxide mixtures

The effect of carbon dioxide (CO₂) concentration on the ignition behaviour of hydrocarbon and CO₂ gas mixtures is examined in both jets and confined explosions. Results from explosion tests are presented using a 20 l explosion sphere and an 8 m long section of 1.04 m diameter pipeline. Experiments to assess the flame stability and ignition probability in free-jets are reported for a range of different release velocities. An empirically-based flammability factor model for free-jets is also presented and results are compared to ignition probability measurements previously reported in the literature and those resulting from the present tests.The results help to understand how CO₂ changes the severity of fires and explosions resulting from hydrocarbon releases. They also demonstrate that it is possible to ignite gas mixtures when the mean concentration is outside the flammable range. This information may be useful for risk assessments of offshore platforms involved in carbon sequestration or enhanced oil recovery, or in assessing the hazards posed by poorly-inerted hydrocarbon processing plant.     

Evaluation of an in-vehicle monitoring system (IVMS) to reduce risky driving behaviors in commercial drivers: Comparison of in-cab warning lights and supervisory coaching with videos of driving behavior

ProblemRoadway incidents are the leading cause of work-related death in the United States.MethodsThe objective of this research was to evaluate whether two types of feedback from a commercially available in-vehicle monitoring system (IVMS) would reduce the incidence of risky driving behaviors in drivers from two companies. IVMS were installed in 315 vehicles representing the industries of local truck transportation and oil and gas support operations, and data were collected over an approximate two-year period in intervention and control groups. In one period, intervention group drivers were given feedback from in-cab warning lights from an IVMS that indicated occurrence of harsh vehicle maneuvers. In another period, intervention group drivers viewed video recordings of their risky driving behaviors with supervisors, and were coached by supervisors on safe driving practices.ResultsRisky driving behaviors declined significantly more during the period with coaching plus instant feedback with lights in comparison to the period with lights-only feedback (ORadj = 0.61 95% CI 0.43–0.86; Holm-adjusted p = 0.035) and the control group (ORadj = 0.52 95% CI 0.33–0.82; Holm-adjusted p = 0.032). Lights-only feedback was not found to be significantly different than the control group's decline from baseline (ORadj = 0.86 95% CI 0.51–1.43; Holm-adjusted p > 0.05).ConclusionsThe largest decline in the rate of risky driving behaviors occurred when feedback included both supervisory coaching and lights.Practical applicationsSupervisory coaching is an effective form of feedback to improve driving habits in the workplace. The potential advantages and limitations of this IVMS-based intervention program are discussed.     

Characterization of heavy metals in fly ash from municipal solid waste incinerators in Shanghai

This study aims to develop a methodology for analysis of characteristics of heavy metals in MSWI fly ash. It performed analysis of composition of heavy metals, leaching toxicity, leaching behavior as a function of pH, specification distribution and corresponding mineral components of residue derived from each step of the sequential extraction. It is found that content of heavy metals follows the sequence of Zn > Pb > Cu > Cr > As > Ni > Cd approximately Hg in both plants, and that total heavy metals account for less than 1% by mass of fly ash. Major hazardous heavy metals in fly ash are As, Cd, Hg, Pb and Zn, whose leaching ratios exceed the limit value described in hazardous waste identification standard. Measured leaching results of Cu, Pb and Zn are essentially consistent with the simulated results at pH between 0 and 13. Content of calcium-silicates, alumino-silicates and glass phases in residue derived from sequential extraction procedure increases steadily from the first step to the fifth step of the sequential extraction procedure. Cu, As, Cr, Hg, Cd, and Ni, relatively stable under strong basic conditions, can be leached out under strong acidic conditions, while Zn and Pb tend to be leached out under both strong acidic and basic conditions.     

Magnetophoretic separation of Chlorella sp.: Role of cationic polymer binder

Cationic polyelectrolyte promoted effective attachment of iron oxide nanoparticles (IONPs) onto microalgal cells through electrostatic attraction. Poly(diallyldimethylammonium chloride) (PDDA) and chitosan (ChiL), both are cationic polymer, are feasible to act as binding agent to promote rapid magnetophoretic separation of Chlorella sp. through low gradient magnetic separation (LGMS) with field gradient ▿B less than 80 T/m in real time. Cell separation efficiency up to 98% for the case of PDDA and 99% for the case of ChiL can be achieved in 6 min when 3 × 10⁷ cells/mL Chlorella sp. are exposed to 300 mg/L surface functionalized-IONPs (SF-IONPs). Different polyelectrolytes do not give significant effect on cell separation efficiency as long as the particle attachment occurred. However, the PDDA is more preferable as the binder for all type of microalgae medium than the chitosan (ChiL) since it is not pH dependent. SF-IONPs coated with PDDA guarantee the cell separation performance for all pH range of cell medium, with 98.21 ± 0.40% at pH 8.84. On the other hand, the ChiL performance will be affected by the cell medium pH, with only 22.93 ± 31.03% biomass recovery at pH 9.25.     

An explosion of a tank car carrying waste hydrogen peroxide

On the Metropolitan Expressway in Tokyo, a tank car exploded because it was carrying hydrogen peroxide (H₂O₂) in a compartment in which copper chloride (CuCl₂) remained. Although the main cause of the accident was trivial, the background on the accident suggested that an induction period in the reaction led to a mistake. This report describes the experimental investigation of the catalytic ability of CuCl₂, and comparing it with two other copper(II) compounds (nitrate: Cu(NO₃)₂; and copper sulfate: CuSO₄) and three iron(III) compounds (chloride: FeCl₃; nitrate: Fe(NO₃)₃; and sulfate: Fe₂(SO₄)₃).The experiments were performed using a reaction calorimeter. During the experiments at 35 °C, 2×10⁻⁵ mol of copper compounds slowly reacted with H₂O₂ and generated a precipitate. The iron compounds allowed the hydrogen peroxide to violently decompose. A 1×10⁻⁴ mol solution of CuCl₂, however, produced a violent decomposition at 35 °C. At 15 °C, a moderate heat release occurred.Based on these results, the concentration and temperature dependence of the catalytic ability of CuCl₂ were postulated to contribute to the induction period observed in the accident.     

Stochastic modeling of accident risks associated with an underground coal mine in Turkey

In this study, a methodology is proposed towards development of an uncertainty model that includes randomness in the occurrence of days-lost accidents in a coal mine. The accident/injury data consists of 1390 days-lost accident cases recorded at GLI-Tuncbilek underground lignite mine from January 1994 to December 2002. In the first step of proposed methodology, the frequency and the severity of the accidents have been modeled statistically by fitting appropriate distributions. The test done by BestFit software yields a chi-square value of 21.53 (p = 0.089) with 14 degrees of freedom and estimates the parameter of lambda for Poisson distribution as 12.87 accidents/month. For the severity component, a lognormal distribution is fitted to days-lost data and chi-square goodness-of-fit test calculates a value of 40.44 (p = 0.097) with 30 degrees of freedom. The parameters of lognormal distribution are estimated as a mean of 14.3 days and standard deviation of 23.1 days, respectively. Then, two distributions are basically combined by Monte Carlo simulation in order to construct relative risk levels in yearly base referring to the final cumulative distribution. Finally, a simple forecasting modeling is carried out in order to quantitatively predict the expected risk levels by using decomposition technique in time series analysis. Stochastic model estimates that although, there would be substantial reduction in the expected number of accidents in the near future, the higher level of risks still should be a concern for the mine management.     

Investigations of flame front propagation between interconnected process vessels. Development of a new flame front propagation time prediction model

For the case where a dust or gas explosion can occur in a connected process vessel, it would be useful, for the purpose of designing protection measures and also for assessing the existing protection measures such as the correct placement, to have a tool to estimate the time for flame front propagation along the connecting pipe. Measurements of data from large-scale explosion tests in industrially relevant process vessels are reported. To determine the flame front propagation time, either a 1 m³ or a 4.25 m³ primary process vessel was connected via a pipe to a mechanically or pneumatically fed 9.4 m³ secondary silo. The explosion propagation started after ignition of a maize starch/air mixture in the primary vessel. No additional dust was present along the connecting pipe. Systematic investigations of the explosion data have shown a relationship between the flame front propagating time and the reduced explosion over-pressure of the primary explosion vessel for both vessel volumes. Furthermore, it was possible to validate this theory by using explosion data from previous investigations. Using the data, a flame front propagation time prediction model was developed which is applicable for:

• •gas and dust explosions up to a K value of 100 and 200 bar m s⁻¹, respectively, and a maximum reduced explosion over-pressure of up to 7 bar;
• •explosion vessel volumes of 0.5, 1, 4.25 and 9.4 m³, independent of whether they are closed or vented;
• •connecting pipes of pneumatic systems with diameters of 100–200 mm and an air velocity up to 30 m s⁻¹;
• •open ended pipes and pipes of interconnected vessels with a diameter equal to or greater than 100 mm;
• •lengths of connecting pipe of at least 2.5–7 m.

     

Association between safety leading indicators and safety climate levels

ObjectivesThe aim of this study was to evaluate the association of leading indicators for occupational health and safety, particularly safety inspections and non-compliances, with safety climate levels.MethodsNordic Occupational Safety Climate Assessment Questionnaire was employed to evaluate safety climate in cross-sectional design. The geographically diverse population of the inspection body made it possible to conduct the survey across 10 provinces in Iran. 89 completed questionnaires were obtained with a response rate of 47%. Except for management safety justice, the internal consistency of other six dimensions was found to be acceptable (α ≥ 0.7).ResultsMean scores of dimensions ranged from 3.50 in trust in the efficacy of safety systems (SD = 0.38) to 2.98 in workers' safety priority and risk non-acceptance (SD = 0.47). Tukey HSD tests indicated a statistically significant difference of mean scores among groups undergoing different number of safety inspections and those receiving different number of non-compliances (p < 0.05), with no significant differences based on safety training man-hours and sessions (p > 0.05). Spearman's rank-order correlation showed no relationship between work experience and number of non-compliances (correlation coefficient = − 0.04, p > 0.05) and between safety training man-hours and number of non-compliances (correlation coefficient = − 0.15, p > 0.05).ConclusionsOur results indicate that safety climate levels are influenced by number of safety inspections and the resultant non-compliances.Practical applicationsFindings suggest that safety non-compliances detected as a result of conducting safety inspections could be used to monitor the safety climate state. Establishing plans to conduct scheduled safety inspections and recording findings in the form of safety non-compliance and monitoring their trend could be used to monitor levels of safety climate.     

Predicting the maximum gas deflagration pressure over the entire flammable range

This paper describes a semi-empirical method to predict the maximum pressure for fuel/air deflagrations over the entire flammable range. The method is based on availability, which is a thermodynamic concept representing the maximum mechanical energy extractable from a given mass of material. In total eight fuel/air systems were considered — the deviation between the predicted and experimental maximum pressure is from −20 psia to +15 psia. This is a significant improvement over ideal gas or equilibrium prediction methods.