Driving around turbo-roundabouts vs. conventional roundabouts: Are there advantages regarding pollutant emissions?

• Autor(a) principal: Fernandes, Paulo
• Data de Publicação: 2016
• Outros Autores: Pereira, S. R., Bandeira, J. M., Vasconcelos, Luís, Bastos Silva, Ana
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.19/3157
• topic: Turbo-roundabouts; Multi-lane roundabouts; Speed Profiles; Discrete Models; Emissions

This paper addresses the impact of turbo-roundabouts located in urban areas on pollutant emissions using field measurements of vehicle activity data and road congestion levels. The research also compares the emissions of vehicles moving along a turbo-roundabout and a conventional multi-lane roundabout. Based on field measurements taken at turbo-roundabouts without curb dividers located in Grado (Spain) and multi-lane roundabouts in Aveiro (Portugal), three representative speed profiles for each speed trajectory were identified: no stop (I), stop once (II), and multiple stops (III). This study also develops discrete models for turbo-roundabouts and multi-lane roundabouts in which the relative occurrence of those speed profiles is expressed as a function of the entry and conflicting traffic flows. The Vehicle Specific Power (VSP) methodology is then employed to estimate second-by-second pollutant emissions. This study tests the hypotheses that emissions are impacted by the differences in: 1) the characteristics of speed profiles in each movement; 2) the volumes of entry and conflicting flows; 3) the overall saturation level; and 4) the transportation facility considered (turbo-roundabout /multi-lane roundabout). Considering the selected case studies and traffic demands, vehicles at turbo-roundabouts generated more emissions (15-22%, depending on the pollutant) than multi-lane conventional roundabouts, especially under medium and high congested levels. These findings suggest that there are no advantages in implementing turbo-roundabouts from an environmental point of view, even in no saturated conditions.