Air quality in urban areas is strongly influenced by exhaust emitted by the public transport fleet. The aim of this study was to analyze benefits in the fuel consumption, fuel costs and exhaust emissions when replacing baseline diesel fueled EURO III city buses by the compressed natural gas (CNG)-fueled EURO V buses and by hydraulic series hybrid diesel-fueled EURO V buses. Real-world measurements were performed on the regular bus route to access realistic energy consumption and exhaust emissions. Instantaneous gaseous emission (CO₂, CO, NO_x and THC) were measured together with the instantaneous PM₁₀ mass emission. Innovativeness of the presented approach thus arises from the systematic comparison of different powertrain technologies under real-world drive cycles and measuring time traces of not only gaseous but also of PM₁₀ mass emissions. Furthermore, lumped cycle averaged emissions are interpreted and explained by typical powertrain performance parameters and exhaust emission time traces. Cumulative results indicate that application of the CNG fueled buses does not necessary reduce CO₂ emissions compared to diesel-fueled buses whereas reduction in fuel costs is evident. Additionally, it is shown that hybrid operation of the hydraulic series hybrid diesel-fueled bus resulted in higher fuel consumption due to poorly optimized hybrid topology and control strategy. Furthermore, analyses of the time traces point out inadequate lambda control of CNG-fueled buses and nucleation mode-based particle number emissions during deceleration.

Managers' commitment to safety has been recognized as a focal concept that can play an important role as organizations strive to improve safety performance and prevent major accidents. When management is committed to safety, this shows employees that safety is an important value to the organization, which, in turn, affects employees' safety behavior. Although the number of studies that explore the concept of safety commitment has considerably increased in recent years, the main question that remains to be answered is how managers can most effectively demonstrate their commitment to safety to employees and through what mechanisms. In this paper, we examined the relationship between managers' commitment to safety and employees' perceptions of managers' commitment to safety, with a specific focus on the potential mediating effect of managers' leadership style. To explore the proposed relationship, we performed an explanatory quantitative study on a sample of 147 respondents from six safety-critical organizations in the EU. By employing a mediation model, we were able to gain a better understanding of the role that transformational leadership can play when managers demonstrate their safety commitment to employees. The results showed a positive and significant relationship between managers' commitment to safety and employees' perceptions of managers' commitment to safety. Furthermore, we found a statistically significant difference between managers' and employees' perceptions. The mediation analysis also confirmed that leadership style mediates the relationship between managers' commitment to safety and employees' perceptions of managers' commitment. This paper adds to the understanding of how managers can demonstrate their commitment to safety through their leadership and how managers' leadership style helps to shape employees' perceptions. The findings highlight the relevance of managers' safety commitment and transformational leadership style for employees' perceptions of managers' safety commitment, which is a known antecedent of safety performance.