Estimation of Reliability Parameters of a Complex Repairable System

In this paper estimation of reliability parameters of a complex repairable system is considered and semi-markov process is used in analyzing various reliability parameters such as Transition Probabilities, Mean sojourn times, MTSF, Availability and Busy period of repairman in repairing the failed units. In the past, Arora et-al[2] has done reliability analysis of two unit standby redundant system with constrained repair time. Gupta et-al [6] has worked on a compound redundant system involving human failure. Rander et-al [2] has evaluated the cost analysis of two dissimilar cold standby systems with preventive maintenance and replacement of standby units. A pioneer work in this field was done by Gopalan [1] and Osaki [3] by performing analysis of warm standby system and parallel system with bivariate exponential life respectively. Earlier, Pathak et al [7&8] studied reliability parameters of a main unit with its supporting units and also compared the results with two different distributions. In this paper, Chapman-Kolmogorov equations are used to develop recursive relations. Also the involvement of preventive maintenance in the model increases the reliability of the functioning units. In the end a particular case is also taken for discussion

Spatial Variation in Personal Exposure of Parking Attendants to Traffic Emissions in an Urban Conurbation

This study presents temporal and spatial variations in personal exposure of parking attendants in a busy conurbation in the northern part of the UK. Two traffic related pollutants - carbon monoxide (CO) and ultrafine particulates (UFP), mainly associated with urban drives, have been considered for two distinct locations- one, in the city centre and the other in a suburban area of Leeds, a prominent city in West Yorkshire. The monitoring of pollutants was conducted while parking attendants carried out their duty along the streets during different times of the year to capture the seasonal fluctuations. Our results show a wide variation in exposure levels for both CO and UFP, marked both by seasonal and daily characteristics. There seems to be considerable variations in exposure levels depending on the location of the parking attendants with respect to traffic activity. Specifically, the level of exposure closer to market areas within the city centre, despite located in open spaces but closer to congested streets were found to be much higher owing to frequent stopping, stopping and idling of cars in search of parking spaces. This demonstrates the merit in setting up transport interchanges and park-and-ride schemes away from busy streets to ameliorate the exposure levels

The Urinary 1-Hydroxypyrene Biomarker in Street Janitors Exposed to Air Quality Changes Associated with Religious Events in Madinah, Saudi Arabia

Madinah is the second most important Muslim holy city in Saudi Arabia. Exceptionally during holy months, traffic congestion and consequent air emission of several pollutant compounds mainly carcinogenic Benzo[a]pyrene (BaP) is expected to reach high levels at certain places. Inhalation of air BaP emissions is the main route of entry into the human body. Therefore, the aim of the present study was to assess a biomarker of exposure to air BaP which is urinary 1-hydroxypyrene (1-OHP) among janitors and find out the relation between this biomarker with daily exposure to air BaP, some traffic and weather factors

Development of multi-functional streetscape green infrastructure using a performance index approach

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.This paper presents a performance evaluation framework for streetscape vegetation. A performance index (PI) is conceived using the following seven traits, specific to the street environments – Pollution Flux Potential (PFP), Carbon Sequestration Potential (CSP), Thermal Comfort Potential (TCP), Noise Attenuation Potential (NAP), Biomass Energy Potential (BEP), Environmental Stress Tolerance (EST) and Crown Projection Factor (CPF). Its application is demonstrated through a case study using fifteen street vegetation species from the UK, utilising a combination of direct field measurements and inventoried literature data. Our results indicate greater preference to small-to-medium size trees and evergreen shrubs over larger trees for streetscaping. The proposed PI approach can be potentially applied two-fold: one, for evaluation of the performance of the existing street vegetation, facilitating the prospects for further improving them through management strategies and better species selection; two, for planning new streetscapes and multi-functional biomass as part of extending the green urban infrastructure

Investigation of older driver's takeover performance in highly automated vehicles in adverse weather conditions

Driving is important for older people to maintain mobility. To reduce age-related functional decline, older drivers may adjust their driving by avoiding difficult situations. One of these situations is driving in adverse weather conditions such as in the rain, snow and fog which reduce the visual clarity of the road ahead. The upcoming highly automated vehicle (HAV) has the potential of supporting older people. However, only limited work has been done to study older drivers' interaction with HAV, especially in adverse weather conditions. This study investigates the effect of age and weather on takeover control performance among drivers from HAV. A driving simulation study with 76 drivers has been implemented. The participants took over the vehicle control from HAV under four weather conditions clear weather, rain, snow and fog, where the time and quality of the takeover control are quantified and measured. Results show age did affect the takeover time (TOT) and quality. Moreover, adverse weather conditions, especially snow and fog, lead to a longer TOT and worst takeover quality. The results highlighted that a user-centred design of human-machine interaction would have the potential to facilitate a safe interaction with HAV under the adverse weather for older drivers

Continuous increases of surface ozone and associated premature mortality growth in China during 2015-2019

Ambient ozone (O3) pollution has become a big issue in China. Recent studies have linked long- and short-term O3 exposure to several public health risks. In this study, we (1) characterize the long-term and short-term O3-attributed health metric in China from 2015-2019; (2) estimate the surface O3 trends; and (3) quantify the long-term and short-term health impacts (i.e. all-cause, cardiovascular and respiratory mortality) in 350 urban Chinese cities. In these 5-years, the national annual average of daily maximum 8h average (AVGDMA8) O3 concentrations and warm-season (April−September) 4th highest daily maximum 8h average (4DMA8) O3 concentrations increased from 74.0±15.5 μg/m3 (mean±standard deviation) to 82.3±12.0 μg/m3 and 167±37.0 μg/m3 to 174±30.0 μg/m3 respectively. During this period, the DMA8 O3 concentration increased by 1.9±3.3 μg/m3/yr across China, with over 70% of the monitoring sites showing a positive upward trend and 19.4% with trends >5 μg/m3/yr. The estimated long-term all-cause, cardiovascular and respiratory premature mortalities attributable to AVGDMA8 O3 exposure in 350 Chinese cities were 181,000 (95% CI: 91,500-352,000), 112,000 (95% CI: 38,100-214,000) and 33,800 (95% CI: 0-71,400) in 2019, showing increases of 52.5%, 52.9% and 54.6% respectively compared to 2015 levels. Similarly, short-term all-cause, cardiovascular and respiratory premature mortalities attributed to ambient 4DMA8 O3 exposure were 156,000 (95% CI: 85,300-227,000), 73,500 (95% CI: 27,500-119,000) and 28,600 (95% CI: 14,500-42,800) in 2019, increases of 19.6%, 19.8% and 21.2% respectively compared to 2015. The results of this study are important in ascertaining the effectiveness of recent emission control measures and to identify the areas that require urgent attention

Investigation of older drivers’ requirements of the human-machine interaction in highly automated vehicles

The population of older drivers is increasing in size. However, age-related functional decline potentially reduce their safe driving ability and thereby their wellbeing may decline. Fortunately, the forthcoming highly automated vehicles (HAVs) may have the potential to enhance the mobility of older drivers. HAVs would introduce a revolutionary human-machine interaction in which drivers can be completely disengaged from driving, and their control would be required occasionally. In order to inform the design of an age-friendly human-machine interaction in HAVs, several semi-structured interviews were conducted with 24 older drivers (mean = 71.50 years, SD = 5.93 years; 12 female, 12 male) to explore their opinions of and requirements towards HAV after they had hands-on experience with a HAV on a driving simulator. Results showed that older drivers were positive towards HAVs and welcomed the hands-on experience with HAVs. In addition, they wanted to retain physical and potential control over the HAVs, and would like to perform a range of non-driving related tasks in HAVs. Meanwhile, they required an information system and a monitoring system to support their interactions with HAVs. Moreover, they required the takeover request of HAVs to be adjustable, explanatory and hierarchical, and they would like the driving styles of HAVs to be imitative and corrective. Above all, this research provides recommendations to inform the design of age-friendly human-machine interactions in HAVs and highlights the importance of considering the older drivers’ requirements when designing and developing automated vehicles

Public attitudes to and perceptions of high speed rail in the UK

With the planned expansion of high speed rail (HSR) in the UK, demand for longer-distance travel is expected to increase significantly over the coming decades. This paper presents a study into attitudes and perceptions of long distance travel in the UK, particularly in relation to HSR. A questionnaire was developed to investigate attitudes to travelling long distances and to HSR, importance of journey characteristics and current travel behaviours. A factor analysis of 46 attitude items yielded six factors: travel security, improvement to road and air, prestige of HSR, comfort, negative aspects of HSR and the usefulness of travel time. Analyses showed significant demographic and travel characteristic differences across the factors. There was also evidence of a more negative impact and lower prestige for people living closer to proposed HSR routes. Willingness to pay for travel time saved was related to a number of journey characteristics but the utility of time was also important. The findings are considered in light of theories of attitude change, attitudes to travel and sustainability and the implications for the future development of HSR policy, particularly in terms of balancing increased fares with utility of travel time

Investigating the effects of age and disengagement in driving on driver’s takeover control performance in highly automated vehicles

Driving is closely linked to older people’s mobility and independence. However, age-related functional decline reduces their safe driving abilities and thereby their wellbeing may decline. The rapid development of vehicle automation has the potential to enhance the mobility of older drivers by enabling them to continue driving safer for longer. So far only limited work has been carried out to study older drivers’ interaction with highly automated vehicles (HAV). This study investigates the effect of age and level of driving disengagement on the takeover control performance in HAV. A driving simulation study with 76 drivers has been conducted. Results showed that 20 s was sufficient for drivers to take over control from HAV. Older drivers take longer to respond and make decisions than younger drivers. The age effect on some aspects of takeover quality, in terms of operating steering wheel and pedals, is still pronounced. In addition, complete disengagement in driving in HAV leads to a longer takeover time and worse takeover quality, and it affects older drivers more seriously than younger drivers. The results highlight that an age-friendly design of human-machine interaction is important for enhancing the safety and comfort of older drivers when interacting with HAVs

Fork in the road: In-vehicle navigation systems and older drivers

A significant characteristic of the UK's rapidly ageing population is the high percentage of older adults who rely extensively on their private automobile to stay mobile. There are, however, functional declines that occur with ageing that affect an individual's ability to drive safely. Additionally, navigating becomes more difficult as we age and can result in older adults reducing their driving on unfamiliar routes. Thus, understanding how older drivers currently plan and then way-find journeys will allow future in-vehicle navigation systems to be more appropriate for the needs of older adults. This paper reports on the findings of six focus groups with older drivers; three groups with those who use in-vehicle navigation systems and three groups with those who do not. The focus groups found that the use of in-vehicle navigation systems provide older drivers with an increased confidence on the roads, a form of companionship in the car and an element of pleasure in driving. When planning long distance trips, older drivers will use online planning tools that provide an initial familiarity with their traditional method of navigation. Some participants who do not currently use any driving aids reported the use of potentially unsafe navigating behaviours to assist them on road network indicating a clear need for assistance in navigating. Finally, there are some significant barriers for in-vehicle navigation systems to overcome before they can be considered beneficial for older drivers