How effective are traffic limiting measures at improving air quality? : a study of the Maltese context

Abstract

The urban environment in Malta faces escalating challenges resulting from population growth and an increase in vehicular traffic, congestion and poor air quality. Consideration is given to the traffic and air quality situation in the Maltese context, and the adverse health effects linked to traffic generated air pollution. This research addresses these issues by exploring the application and effectiveness of traffic limiting measures as a means to improve air quality. By investigating international best practices and existing local policies, it was found that the application of ‘push’ measures was a recommended approach to reduce private vehicle usage and promote sustainable transportation alternatives. The methodology involved applying and testing similar measures within a defined section of the Maltese road network. The main testing methodology utilised a digital toolset, composed of microsimulation traffic modelling, emission modelling and air dispersion modelling. A microsimulation traffic model of a selected area in Malta was constructed to simulate the traffic situation before and after the implementation of proposed traffic limiting measures. Subsequently, data extracted from the traffic model was used in emission and air dispersion modelling software to evaluate the effectiveness of the proposed strategies in improving air quality. The modelling results show that the tested measures, which involved the limiting of private vehicle use and access, saw a decline in traffic performance and/or small variations in pollutant concentrations. Through this analysis, the study concluded that introducing minor-scale strategies that simply limit vehicle traffic on small parts of the road network can result in negligible impact on air quality. Additionally, the importance of the vehicle fleet composition was shown to be also vital. In future, consideration should be given to testing broader strategies that improve capacity for other, cleaner modes of transport, along with limiting access to polluting private vehicles. Ultimately, the modelling process outlined in this study can be used by decision makers to test other types of measures aimed at reducing traffic-generated emissions, in order to find the most effective strategies, especially with the introduction of more stringent air quality standards.