Evaluation of vehicular emissions reduction strategies using a novel hybrid method integrating BWM, Q methodology and ER approach

Road transportation is the main source of greenhouse gas (GHG) emissions in Iran. Different road transport emissions reduction strategies (RTERS) can be defined to address this environmental problem. The present study aims to define a comprehensive set of RTERS according to the socio-economic conditions of Iran. Then, the defined strategies are evaluated using a new hybrid decision-making technique developed by integrating the conventional Q-methodology (QM), best–worst method (BWM) and evidential reasoning (ER) approach. The main advantages of the developed methodology include: simple Q-sorting, the capability of checking inconsistency ratio of judgments and dealing with uncertainty. A set of thirty-three RTERS was defined and then categorized into the following seven main strategies, including travel demand management (TDM), public transport management (PTM), traffic flow management (TFM), education, urban planning and development (UPD), and governmental rules and regulations (GRR). These strategies were assessed based on the views of twenty-three experts and government officials. Five perspectives on the importance of RTERS were derived using BWM and QM: 1—PTM-FCM, 2—UPD, 3—TDM, 4—FCM-PTM and 5—FCM. Finally, the ER approach was employed to aggregate these viewpoints. The aggregated perspective highlights that improving fuel quality and HOV systems are the most effective RTERS, while the mitigation policies based on deterrent rules and regulations are the least effective strategies. Accordingly, some managerial implications and suggestions are provided in this study.