Estimation Of Turbo-Roundabout Capacity

In recent years, a new estimation method of lane capacity at turbo-roundabouts entries in various countries has been developed. It can be shown that methods developed under different assumptions and taking into account various factors determining capacity give significantly different results. Different approaches to the estimation of capacity are used, i.e.: stream conflict models (regression models) and gap acceptance models with behavioural parameters. The values of parameters in models reflect local research conditions. Therefore, the direct application of empirical findings on another area (country) may cause an unspecified inaccuracy. The authors conducted a comparison of capacity estimation models, i.e.: those developed by Fortuijn and Harte, HCM2010 Hagring and Fisk, and Brilon and Wu, in order to indicate differences of estimated capacity. The paper also presents research conducted in Poland, including: parameters of the gap acceptance capacity model (critical headway, follow-up headway) as well as characteristics of a roundabout circulating stream. These parameters were used in a comparative study of models which are used in various countries to estimate the capacity of roundabout entries. The main aim of this research is the development of an estimation capacity method for practical applications in Poland. The fmdings and analyses are promising, but they indicate a need for continued research, in particular in behavioural parameters of the gap acceptance model.