Browsing by Author "Wei, Chia"
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Item Bus Driver Intersection Task Analysis: Investigation of Bus-Pedestrian Crashes(Intelligent Transportation Systems Institute, Center for Transportation Studies, University of Minnesota, 2013-01) Wei, Chia; Becic, Ensar; Edwards, Christopher; Manser, MichaelThe current report includes two specific research efforts. The primary objective of the first research effort was to conduct a task analysis of a left-turn maneuver by a bus driver. The goal of this task analysis was to provide insight into the cognitive and perceptual processes that bus drivers complete while performing a left-turn maneuver. An additional goal of the first research effort included the development of potential countermeasures that could help reduce the frequency of bus-pedestrian collisions. The interviews conducted as part of the task analysis revealed that drivers engage in a large number of subtasks and cognitive/perceptual processes when completing a left-turn maneuver. We proposed two potential interventions for the reduction of bus/pedestrian collisions. One of the proposed interventions was designed to aid a driver in detection of pedestrians at a crosswalk. The second intervention was designed to remove a need to perform a particular attention-demanding subtask to reduce the cognitive and perceptual load that drivers experience during this maneuver. The second research effort was designed as a pilot simulator study in which we examined the potential effectiveness of proposed interventions. The second study uncovered unanticipated findings (i.e., high rate of collisions with pedestrians) that may be due to the nature of the simulator studies – lack of real-world consequences. The results of the pilot study provided sufficient data for further examination of different support tools for the reduction of the fatalities between left-turning buses, and also uncovered potential relationship between work-related stress and the impact on driving performance.Item Incidence of and Risk factors for occupational injury among transit bus operators(2014-05) Wei, ChiaDriving a bus, professionally, is recognized as a high-risk occupation. This particular occupation has long working hours, irregular schedules, and lack of scheduled time for breaks and meals. Studies have shown professional bus operators have a high risk of cardiovascular disease, hypertension, gastrointestinal disorders and musculoskeletal problems, as well as psychological health issues, including fatigue, depression and anxiety. Based on Karasek's psychological demands/decision model, all of the working characteristics for bus operators result in high workload demand and low job control. Stress is reported as a main risk factor that leads to adverse health outcomes among professional drivers, especially cardiovascular disease and gastrointestinal disorders. Another serious stressor is the risk of violent acts. Bus operators are at potential risk of exposure to work-related violence as part of the requirement to interact with passengers. Numerous studies focused on bus operators' occupational diseases have provided a basic understanding for this study. Thus, the objective of this study was to provide a more comprehensive understanding of the magnitude, potential risk factors, and protective factors that may be associated with occupational injuries (both unintentional and intentional injuries) among bus operators and can serve as a basis for possible intervention strategies to reduce injuries.Demographic, work-related, and injury information was obtained from a transit company for a five-year period (Dec 1, 2006 to Dec 31, 2011). These data included the bus operators' demographic information: gender and age; work-related characteristics: years of working; job classification (part-time or full-time); working hours per day; driving hours per day; overtime hours per day; bus garage division; work start time; shift schedule; number of busses driven per day; and bus route types. Injury event reports included type of injury and body part(s) affected. Estimates of rates, per 100 Full Time Equivalents (FTEs), and associated 95% Confidence Intervals (C.I.), were generated using generalized estimating equations (GEEs) with exchangeable working correlation matrices. Adjusted Hazard Ratios (HRs), with associated 95% C.I., were generated, using Cox Proportional Hazards models. A total of 2,095 bus operators was included in this study. The overall unintentional injury rate with 95% C.I. was 17.8 (16.1-19.7) per 100 FTEs. Multivariable analysis identified increased risks for operators who: were female, compared to male (HR=2.4; 2.0-2.8); worked less than seven, compared to seven to less than 12 hours per day (HR=4.6; 3.8-5.5); and drove less than seven compared to seven to less than 12 hours per day (HR=3.2; 2.7-3.8). Operators who worked split, versus straight shifts, demonstrated a suggestive increased risk (HR=1.2; 1.0-1.4). Bus operators also tended to have an increased risk when driving limited versus regular bus routes (HR=1.36; 1.0-1.8). For intentional injury, the overall injury rate with 95% C.I. was 1.4 (1.1-1.7) per 100 FTEs. Operators who commenced working between 3 p.m. and 6 p.m. (HR=2.4; 1.2-5.1) and 12 a.m. and 3 a.m. (HR=5.3; 1.6-18.2), had higher risks of intentional injury, compared to those who commenced work between 9 a.m. and 12 p.m. In addition, higher risks were also found for operators who: worked less than seven or more than 12 hours (HR=16.3; 9.5-28.1 and HR=9.6; 3.7-23.5, respectively), compared to seven to less than 12 hours; drove less than seven hours or more than 12 hours (HR=11.3; 6.6-19.5 and HR=11.9; 4.8-29.6, respectively), compared to seven to less than 12 hours. Moreover, those who worked overtime had 30% higher risks, compared to those who did not.Results of this study serve as a basis for further studies and can inform the development of targeted intervention strategies to reduce occupational injuries relevant to bus operators.Item Violence against educators.(2011-09) Wei, ChiaIntroduction Physical and non-physical violence are recognized as a major public health issue in the work environment and one commonly ignored population that may experience work-related violence is teachers/educators. However, to date, there has been no apparent investigation to examine the relations between various exposures of interest and rates of violence, based on hours worked by educators. The objective of the current study was to identify the potential risks for both physical assault (PA) and nonphysical violence (NPV) against licensed Minnesota educators, based on hours exposed. Methods The target study population was licensed kindergarten through grade 12 educators in Minnesota, who were identified in the Minnesota Department of Education database as of 2003. A random sample of 26,000 educators was selected from this database to determine eligibility; 6,469 eligible participants were included in the study. Data were collected between April 27, 2005 and March 31, 2006, using specially designed mailed questionnaires. PA and NPV event data were collected from respondents for a 12-month time period prior to their respective survey completion dates. Injury rates per 100,000 working hours were calculated, using generalized linear models with Poisson distribution for both PA and NPV events among educators. Multivariate analyses utilized calculated rate ratios to determine the strength of the association between exposures of interest and injury outcomes (PA and NPV); selection of confounders for multiple regression with Poisson distribution was based on Directed Acyclic Graphs, following the methods described by Greenland and colleagues. Results Among all eligible respondents, the majority was female (77%). The total NPV rates were higher than the total PA rates (26.37 and 5.31, respectively). For the four subcategories of NPV, the total rates were: threat (34.82); sexual harassment (7.58); verbal abuse (55.48); and bullying (19.62). Multivariate analyses for respective PA and NPV models revealed increased rate ratios for: educators who were not married (1.28, 1.20) versus married; worked in public alternative (1.73, 1.93), compared to public schools; those who worked in special education (4.39, 1.45) and in multiple activities (4.01, 1.41), compared with standard classroom teaching; and worked with class sizes less than ten (2.71, 1.43), compared to ten to < 25 students. Decreased risks for respective PA and NPV models were identified for: males (0.73, 0.85), compared with females; those who worked as educators for 20-29 (0.66, 0.66), and >30 (0.55, 0.60) years, compared to less than ten years; and worked in their current school for more than 20 (0.39, 0.80) versus less than five years. Conclusions Results from this study provided information about factors associated with increased and decreased risks for violence against educators, based on hours exposed. This information provides a basis for further investigation and consideration of possible intervention strategies to reduce violence in the school environment.