The roadways are used simultaneously by passenger cars, trucks, buses, cyclists, pedestrians, etc. This creates a mixed traffic flow environment in which all the traffic participants share the available infrastructure. In addition, there is an increasing number of automated vehicles (AVs) appearing on roadways that are interacting with conventional traffic, which is forming a new type of mixed traffic flow environment.

There is a need for investigating the resulting effects of mixed traffic, and advanced research should be conducted to explore the traffic efficiency and safety in mixed traffic flow environment. Developing better traffic efficiency and safety methodologies, technologies, and policies are critical importance to reduce the traffic congestion, crashes, traffic-related air pollution, and improve the operation reliability of the mixed traffic flow. Enabled by emerging sensing technologies, big data analytics, and recent advances in driving experiments, traffic efficiency and safety research will greatly enhance our scientific understanding of the new interactions and phenomena in a mixed traffic flow environment.

The aim of this Special Issue is to collate original research and review articles with a focus on addressing the crucial aspects of traffic efficiency and safety issues in a mixed traffic flow environment, with particular emphasis on the interactions between motorized vehicles and non-motorized vehicles, passenger cars and trucks, conventional vehicles, and AVs. The Special Issue also welcomes scientific research that develops and refines methodologies and technologies using new sources of data, such as data from GPS, naturalistic driving, connected vehicles, social media, and smart phones.

Potential topics include but are not limited to the following:

• Safety and efficiency performance assessment of mixed traffic flow
• Safety and efficiency modelling of mixed traffic flow
• The resulting effects of mixed traffic flow environment
• Prediction of mixed traffic flow
• Data-driven traffic efficiency and safety monitoring, assessment, and improvement
• Methodological advancement in mixed traffic flow theory
• Mixed traffic flow simulation
• Innovative traffic efficiency and safety data collection, analyzing, and molding using advanced technologies
• Advanced traffic safety and traffic flow efficiency management strategies and policies
• Travel behaviors and activities modelling