Analyzing On The Approach Delay Calculation Method Based On The Arrival Of The First Vehicle

With the rapid development of economy,the motorization level of cities is becoming increasingly higher.Urban intersection is the throat of road traffic,where traffic problems are frequent,so the management and control of urban intersection is very necessary.The real-time and accurate extraction of traffic information parameters is the main precondition of intersection management and control and implementing traffic intelligent control,and the real-time and accurate acquisition of the delay parameters is a key step to evaluate the operation efficiency and signal time optimization of intersections.The research on real-time and accurate acquisition of delay is of great practical significance for evaluation,control management,signal time optimization of intersection and intelligent transportation system.Firstly,the paper introduces the research actuality of intersection delay extraction method and short time traffic parameter prediction,summarize and review the delay extraction methods such as theory analytic method,field investigation method,simulation method,and summarize the existing short term traffic parameter prediction methods.The arrival time of the first vehicle is extracted by video recording,and the arrival time of the first vehicle is analyzed,and the distribution of the arrival time of the first vehicle is fitted.On the basis of summarizing the factors of delay,this paper uses the orthogonal test method to design the test scheme and constructs the simulation platform with VISSIM software,simulates the test scheme of the orthogonal test design,and makes a thorough and careful analysis on the influence factors of the arrival time of the first vehicle.The test results show that the order of factors in the arrival time of the fisrt vehicle is: saturation,vehicle arrival type,intersection spacing,green letter ratio,saturation flow rate and cart rate.Secondly,the paper constructs the wavelet analysis-elman neural network forecast model to predict the time of the first vehicle arriving at the intersection in each cycle,and the prediction results show that this model can predict the arrival time of the first vehicle in the intersection accurately,and then the validity of the model is verified,and lay the foundation for the construction of the delay extraction model.Finally,the paper introduces two kinds of delay investigation methods.And the measured approach delay of per cycle were extracted.The relationship between the arrival of the first vehicle and the approach delay was analyzed,and a delay extraction model based on the arrival of the first vehicle was constructed.After comparing with the precision of the Webster model,the results show that the delay extraction model based on the arrival of the first vehicle can improve the precision of delay calculation to a certain extent,and reduce the influence of vehicle random arrival on the precision of delay calculation.Then the model is applied to signal time optimization,and the real-time control is realized by COM interface connecting VISSIM simulation platform and MATLAB data processing platform.The advantages of the real-time control scheme and the practicability of the delay extraction model based on the arrival of the first vehicle are verified by contrast with the timing control of the Webster method.