Abstract
Before choosing an intersection project design, an important step is to examine the justification of the construction on the basis of defined criteria. One of the key criteria is the analysis of capacity. Large numbers of roundabout capacity models are present in the world, most of them adapted to the conditions of the country they originate from and they need to be calibrated for local conditions. Key parameters for calibration are critical headway and follow-up headway. Follow-up headway can be measured directly in the field, while critical headway cannot be measured, but is estimated. Many critical headway estimation methods exist (over 30) and each of them provides different values. Different values of critical headway result in different capacity estimation values. This raises the question which method provides more realistic estimations under certain conditions. In this paper, four most frequently used critical headway estimation methods (Raff, Maximum likelihood method, Wu, Logit) were selected to be tested by comparison of theoretical capacity models and actual measured capacity at a small urban roundabout.
Highlights
The use of roundabouts in the cities is becoming increasingly popular due to urban sustainability
Large numbers of roundabout capacity models are present in the world, most of them adapted to the conditions of the country they originate from and they need to be calibrated for local conditions
There is a large number of roundabout capacity models in the world, which are grouped into three key groups [2]: 1) Empirical models based on the relationships between geometry and actual measured capacity in certain traffic and road conditions; 2) Analytical gap acceptance models based on understanding the driver behaviour; 3) Microscopic simulation models based on the modelling of vehicle kinematics and interactions
Summary
The use of roundabouts in the cities is becoming increasingly popular due to urban sustainability. There is a large number of roundabout capacity models in the world, which are grouped into three key groups [2]: 1) Empirical models based on the relationships between geometry and actual measured capacity in certain traffic and road conditions; 2) Analytical gap acceptance models based on understanding the driver behaviour; 3) Microscopic simulation models based on the modelling of vehicle kinematics and interactions. None of these model groups fully describes the behaviour of drivers and processes at a roundabout, so the model parameters need to be calibrated to local conditions.
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