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The traffic circle is a common solution which is widely used in urban and rural areas of Turkey. Although, most of the traffic circles are designed to be signal-controlled, some of them are still being used as unsignalised intersections in order to provide higher capacity and better performance particularly in rural areas. Regression analysis and gap acceptance-based models are the most used estimation methods for capacity prediction of unsignalised traffic circles. In this study, an artificial neural network model (ANN) was investigated as a new approach as ANN models have been successfully applied in various other traffic studies. The entry capacity was predicted by using exponential and multiple linear regressions, gap acceptance theory and the feed forward backpropagation algorithm type of ANN. The results were compared with well known models. The ANN model including the geometric parameters was found to be the most reliable estimator with 71·6% of proper predictions when the discrepancy percentages of the predicted versus observed entry flows were examined for the models. The multiple linear regression and gap acceptance models followed the ANN model with proper prediction proportions of 63·3 and 51·6%, respectively. On the other hand, models that included only circulating flow parameters were only found to be acceptable for limited geometric data conditions.

Start-up lost time is an important parameter in perfor-

The performance of public bus lines is generally evaluated by comparing demand and ridership. However, reliability gain or loss by a proposed bus route should also be considered in the decision-making process to ensure a service that is preferable for users and operable for providers. In this study, it is aimed to provide a tool for predicting the reliability of a proposed bus route by considering route layout and traffic conditions. Travel time based reliability is predicted by using a novel nonparametric method, multivariate adaptive regression splines (MARS). Some critical thresholds of route layout parameters that should be considered for higher reliability are found. It is concluded that route lengths longer than 10 km, and number of intersections over 22 considerably decrease whole day based reliability. For peak hour based reliability, the types and numbers of intersections are found to be more efficient than the ones in whole day based model and a reliability regulator impact of roundabout numbers under nine is observed.

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