Studying the impact of AVs on our road infrastructure offers a lot of potential in the transportation domain; one of these issues is how capacity will be affected. This paper presents a contribution to this research area by investigating the impact of AVs on the capacity of single-lane roundabouts using a microsimulation model. For the development of the model, a roundabout situated in Győr (Hungary) was selected and field data on the roundabout geometric characteristics as well as traffic volumes were used. Simulations using Vissim were run for various scenarios based on varying input traffic volumes and market penetration rates of AVs to assess queue lengths. The highway capacity manual (HCM) roundabout model was used to estimate the capacity of the existing roundabout. Values of follow-up times and critical gaps were set to decreasing as the penetration rate of AVs increases. The results demonstrated that 20% and 40% AVs in the flow would increase leg capacities by about 10% and 20%, respectively. Furthermore, a reduction in excessive queue lengths was estimated and capacities and queue lengths were calculated by legs. It was found that these are highly influenced by the distribution of flows among legs, and the share of flows in various directions.

This study examines the influence of Vulnerable Road Users (VRUs), specifically pedestrians and cyclists, on the entry capacity of urban single-lane roundabouts using non-linear regression modeling, with implications for sustainable urban transportation planning. Data were collected at a single-lane roundabout in Győr, Hungary, through video surveillance, capturing interac- tions among vehicles, pedestrians, and cyclists during peak traffic hours. The analysis demon- strated that incorporating pedestrian and cyclist volumes into the capacity models significantly improved predictive accuracy, increasing R² values from 0.5 (vehicles only) to over 0.8 in the extended models. The results indicate that pedestrian and cyclist interactions reduce entry ca- pacity by up to 30 % and 40 %, respectively. ANOVA tests confirmed the statistical significance of these findings (p < 0.0001). By providing a more precise estimation of roundabout entry capacity that accounts for the non-linear effects of VRUs, the refined model supports the development of transportation sys- tems that prioritize sustainable mobility. These findings underscore the critical need to inte- grate VRUs into capacity assessments to inform design modifications that promote safe and efficient multimodal transportation. Such integration facilitates the reduction of vehicular con- gestion and emissions, contributing to improved air quality and urban livability, aligning with broader environmental objectives in sustainable urban development.