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Projeto de investigação
AROUND - Improving Capacity And Emission Models of Roundabouts
Financiador
Autores
Publicações
Driver Behavior Characterization in Roundabout Crossings
Publication . Silva, Ana Bastos; Santos, Sílvia; Vasconcelos, Luís; Seco, Álvaro; Silva, João Pedro
Roundabouts are widely accepted for their safety, capacity and environmental advantages. Although it can be easily recognized that the driver behavior is mostly related with the roundabout geometry. This paper presents a detailed characterization of the driver behavior while crossing three consecutive double-lane roundabouts in an arterial road. Driver behavior was described in three main levels: i) speed profiles; ii) lateral acceleration profiles; iii) roundabout geometry. It is shown that roundabouts can substantially reduce speed in the negotiation zone. The entry speed and influence zone depends on the desired speed in the upstream sections and on the roundabout geometric characteristics.
Estimating the parameters of Cowan’s M3 headway distribution for roundabout capacity analyses
Publication . Vasconcelos, Luís; Silva, Ana Bastos; Seco, Álvaro; Silva, João
Capacity models based on the gap acceptance theory are widely used in unsignalised intersections and roundabout capacity analysis. !ese models are based on the statistical distribution of major vehicle headways. In this "eld, Cowan’s M3 distribution is usually recognized as the most adequate, but the estimation of its parameters is not trivial. In this paper, the main estimation methods are reviewed and a new method (Simultaneous Numerical Estimation – SNE) is proposed. !e SNE method was used to develop a calibrated relation between parameters, using "eld data collected in Portuguese roads and roundabouts. It was determined that the new formula improves capacity estimates, either in one-lane or in two-lane roundabouts. !e paper also addresses the importance of each input variable and parameter in the resulting capacity model, through a sensitivity analyses.
A Comparison of Roundabout Capacity Models
Publication . Vasconcelos, Luís; Seco, Álvaro; Silva, Ana Bastos; Abreu, Tiago; Silva, João P.
In the present study four roundabout capacity models - Siegloch, Cowan M3-1L, Cowan M3-2L and TRL - are presented and compared against microscopic simulation results. The evaluation framework is centered mostly on the characteristics of the entering and circulating traffic and it is shown that the more popular models - TRL and Siegloch, are unable to generate consistent capacity estimates for the whole range of conflicting flows. The models based on Cowan M3 headway distribution are more robust but still they aren't sensible to differences in the vehicles destinations, both in the entry and in the circulating traffic. This aspect is also poorly handled by the microscopic simulation model.
Performance Assessment of Turbo-roundabouts in Corridors
Publication . Silva, Ana Bastos; Mariano, Pedro; Silva, João Pedro
There is a widespread agreement in the scientific community that the transformation of a conventional multi-lane roundabout into a turbo-roundabout results in a significant increase of road safety levels. However there is no consensus regarding its effect in terms of capacity, as there are some authors that point towards a small reduction in capacity, namely in the major roads entries. The concept of turbo-roundabout is quite recent and therefore there are only a few studies of its performance, in particular, when applied in a network or in a corridor. In this context, this paper focuses on the evaluation of the performance of the turbo-roundabout solution, when applied in corridor, compared to a normal double-lane roundabout. The analysis was based on two key components: capacity and pollutant emissions. The work was supported by microsimulation techniques using the AIMSUN software, based on a real case study calibrated and validated for this purpose. It was possible to conclude that the turbo-roundabout performance is strongly influenced by the traffic load of the network, severely losing its performance in oversaturation conditions. The performance of the solution was also particularly sensitive to the traffic directional distribution, both in the entries as well as in the corridor. In global terms, it was found that the results for the environmental indicators follow the progress of the capacity indicators.
Unidades organizacionais
Descrição
Palavras-chave
Roundabouts,Capacity models,Microscopic models,Pollutant emissions, Engineering and technology ,Engineering and technology/Civil engineering
Contribuidores
Financiadores
Entidade financiadora
Fundação para a Ciência e a Tecnologia, I.P.
Fundação para a Ciência e a Tecnologia, I.P.
Fundação para a Ciência e a Tecnologia, I.P.
Programa de financiamento
5876-PPCDTI
Concurso de Projectos de Investigação Científica e Desenvolvimento Tecnológico em todos os Domínios Científicos - 2010
Concurso de Projectos de Investigação Científica e Desenvolvimento Tecnológico em todos os Domínios Científicos - 2010
Número da atribuição
PTDC/SEN-TRA/122114/2010