This thesis presents a program of research exploring the multilevel organisational structure of fleet safety management. The aim of this research was to investigate three current fleet safety initiatives, and individual and contextual factors influencing safe driving behaviour in a work vehicle. Three studies were conducted to achieve this aim. This research utilised a sample of employees from a range of Queensland Government agencies.----- Study one evaluated three current fleet safety initiatives within the Queensland Government. From a sample of fleet co-ordinators (N=24) and drivers (N=88), this study established the extent to which specific psychological processes underlying the fleet safety initiatives were adopted, and the attitude change associated with their use. This study found mixed support for the Hypotheses, with the influence of the fleet safety initiatives on fleet co-ordinators' and drivers' attitude change being consistent with processes associated with the persuasive communication framework, and behaviour management. However, the study found no support for the behavioural management processes hypothesised to underlie the incentive scheme (CPP). The findings of the study suggested that while fleet safety initiatives can have an influence on fleet co-ordinator and driver attitude change, their impact depends on the extent to which safety issues are viewed as relevant, and the extent to which there is reinforcement within the organisational environment to support these safety initiatives. Therefore, the findings from this study, combined with existing research into the impact of safety climate, suggest the workplace context needs to be taken into account. For this reason, study two investigated the role of perceptions of the safety climate, in addition to individual attributes, as predictors of self-reported crash involvement.----- Study two applied a framework incorporating driver attributes, including attitudes towards traffic safety and self-efficacy, and drivers' perceptions of the safety climate, as predictors of self-reported crashes in a work vehicle. Within this framework, drivers' perception of the safety climate, and their individual attributes were conceptualised as antecedents of driving performance, and driver safety motivation and knowledge mediated the relationship between these factors and self-reported crashes. A total of 385 drivers participated in this study, which found motivation to drive safely mediated the relationship between driver attributes and self-reported crashes. The initial analysis did not find a significant relationship between safety climate and safety motivation. However, posthoc analyses exploring this non-significant relationship found managerial safety values could be distinguished from other facets of the safety climate construct. Subsequently, the results indicated managerial safety values predicted safety motivation, when drivers perceived a strong safety climate. This study provided a more thorough understanding of the variables predicting driver behaviour at an individual level of analysis. However, a shortcoming is the study did not consider the various influences impacting on drivers' safety perceptions, and individual attributes within the context of the work environment.----- Study three extended on the framework established in study two, and investigated the contribution of leader attributes to the prediction of drivers' safety perceptions, and individual attributes. The leader attribute measures, specifically, perceptions of the safety climate, motivation, knowledge, and work overload were collected from a sample of fleet co-ordinators (N=52) and supervisors (N=88). Through multi-level analyses, both supervisors and fleet co-ordinators were shown to influence the safety perceptions and individual attributes of individuals who drive work vehicles. Support was found for positive relationships between supervisor safety knowledge, and the individual attributes. However, there was a large amount of variation due to group membership unaccounted for by supervisor safety knowledge and the safety performance factors investigated within the supervisor groups. These findings suggested supervisors may not be interacting with drivers in relation to fleet safety matters, but that other factors associated with work group membership are having an impact on drivers' safety perceptions. In comparison, there was a small amount of variation accounted for by fleet co-ordinator group membership. However, the results suggested the fleet co-ordinator leader attributes accounted for a high percentage of this variation in group membership. Support was found for a positive relationship between fleet co-ordinator safety perceptions, and driver safety perceptions. Other results found fleet co-ordinators were engaging in higher workloads to enhance the safety perceptions, and attitudes towards traffic safety of drivers within their groups.----- Overall, these studies establish a multilevel organisational process of effect, whereby individual and leader attributes, and organisational initiatives all play a role in influencing the safety performance of work-related drivers. The results also indicated an unclear structure in the management of fleet safety, as perceived by drivers, and through the roles and responsibilities of supervisors and fleet co-ordinators. The implications of these results for the management of fleet safety are discussed.