Throughout the world, research into the various aspects and the various types of roundabouts has spanned many decades. During this long period the number of vehicles, their sizes, and speeds have radically changed. The experiences of drivers have also changed over the past decades. These changes have had a strong influence on the evolution of modern roundabouts. The primary influences of capacity and traffic safety as they relate to the layout of modern roundabouts are now mostly known.

However, there are emerging areas in highway design and vehicle industry that could further influence roundabout design and operations: aspects that this Special Issue is planning to address. Such issues include, but are not limited to, the potential for autonomous-interconnected vehicles, new alternative types of roundabouts, provisions for cyclists, and the influences of modern roundabouts on environment. Especially welcome are submissions relating to elderly drivers and impaired pedestrians at modern types of roundabouts.

Potential topics include but are not limited to the following:

• Evaluation and design of new alternative types of roundabouts
• Modeling of crashes and incidents
• Identification of human factor needs as they relate to users with special needs
• Analysis of roundabout features as they relate to capacity, queuing, and geometry
• Assessment of risk and reliability of designs
• Determination of environmental impacts of modern roundabouts
• Analysis and estimation of life-cycle costs
• Accommodation of cyclists and pedestrians
• Application of expert optimization methods in analysis of functional and safety characteristics of roundabouts and roundabout design optimizations