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In order to seek a simple method to predict real-time vehicle queue length, the basic assumption of which traffic flow in transition is divided into two fluids was represented. The equivalent queue length model was developed on the basis of the conservation equation. The concrete expressions under the two cases were argued. The methods of calculating or calibrating parameters were given. To validate the models under the two cases, the simulation schemes for the first case and the survey schemes for the second case were designed. By contrasting the equivalent queue lengths from the models with the actual queue lengths from the schemes, the following results are found. First, the equivalent queue lengths are all longer than the actual queue lengths. Second, the equivalent queue lengths are stable and the actual queue lengths are fluctuating. The conclusions indicate that the equivalent queue length model can quantitively and better describe the congestion level of traffic flow, especially, for congested traffic flow. Computational implementation of the new method is tractable and can be done very effectively, making it suitable for real-time queue length estimation. |
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Keywords:traffic engineering; traffic flow; real-time vehicle queue length; congestion level |
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