Research On The Critical Question Of Left-turn Traffic Organization At Signalized Intersections

The intersection is key point and the difficulty of the transportation management. The left-turn flow of intersection is the primary factor of confliction, affected the through flow passing through. The method of left-turn traffic organization is mainly separates the left-turn flow with other flow in the space and in the time. The traditional method is the establishment special left-turn lane and the left-turn phase reduces affect to the through flow. This method has the very good effect regarding the non-saturation flow, but speaking of the oversaturation stream of vehicles, traditional method already very inaccessibility effect. So, there is some new method to left-turn in domestic and foreign. For instance, when the left-turn lane capacity insufficien causes oversaturation, in the permission's situation, may establish left-turn waiting area; When the traffic flow present the periodicity imbalancly, may establish variable traffic lane, and so on. But these methods so far, do not have the explicit theory basis. The flow, under certain condition, may transform by one organization way into another, this time the flow is one critical state, transforms by one organization way into another condition is the critical condition. The goal of this article is discovering the critical condition of the left-turn traffic organization way, it is the very important theory value and the project significance.Relied on National Key Technology R&D Program and the National Basic Research Program (973 Program) of China. The critical question of left-turn traffic organization at intersection are mainly discussed in the paper. The paper is composed of six chapters. Chapter Two, Three, Four and Five are the focus in the paper, with Chapter Three, Four and Five as the crux. The key parts of individual chapters are as follows:Chapter One Firstly, research background is introduced with the analysis of conflict and capability, and the indication of research intention and meaning of the paper. Then, in light of two aspects as space separation analysis, and time separation integrated analysis, domestic and overseas research achievements on the theme are summarized, which duplicate the left-turn conflict phenomena and left-turn organization. Finally, the contents of the paper and the chapter scheme in the paper are clarified.Chapter Two Firstly, it is analyzed the left-turn conflict characteristic and the capability of signal intersection in light of three aspect as nonexclusive left-turn lane and phase, nonexclusive left-turn lane and exclusive left-turn phase, exclusive left-turn lane and phase. Then summarized the left-turn organization's idea, and has drawn up the left-turn organization's principle, under the principle instruction, proposed the reasonable left-turn organization method.Chapter Three Firstly, divides the delay of two phase signal edintersection into two parts to calculate: one part is the parking line delay, this is caused by the signal control; Another part is the conflict point delay, this is caused by the conflicts. Then, it is established the conflict point delay model according to the queuing theory and gap theory. Through compare the delay under each kind of condition, has obtained left-turn lane and each kind of left-turn phase critical condition.Chapter Four It is analyzed the geometrical form of the intersection and gained geometrical critical condition. It establishes the model of left-turn queuing location based on the accumulation curve and the transportation wave theory. On condition that channelization and signal timing method of intersection is invariable, it finds the volume threshold. If the left-turn vehicle arrives rate is stable in some time,it can gain the minimum green time and maximum red time. Finally, analysis the movement effect of before and after establishing the left-turn waiting area.and prove the critical condition with example.Chapter Five Fistly, it is designed the detector layout plan according the traffic flow characteristics. Then, it determines the variable lane's attribute according to the detector data and proposes the signalized control method of variable lanes. When current variable traffic lane's attribute is left-turn lane, if the left-turn flow has overflowed, explained that even if adds a left-turn lane, the left-turn flow will continue to overflow, and cannot add the left-turn lane, will adjust signal timing plan; If the through flow has the overflowed, explained that added the left-turn lane to cause the through capability to be insufficient, first choose to adjust the signal timing , if the signal timing plan could not satisfy the capability, then change variable traffic lane attribute; If the both have overflowed, explained that regardless of changes the channelization plan or the timing plan, is unable to change the oversaturation condition. Then, compared capability with the different timing, selects the signal timing of maximum capability; Vice versa.. It has established the pre-signal, and has given pre-signal timing method between the different transformation plan. The suggested strategy was verified with simulation software VISSIM. The results showed that this article method may enhance the intersection traveling capability and reduces the delay by comparing with different channelization and control methods.Chapter Six The obtained improvements and the innovative productions are summed up. The issues to be discussed further are put forward. The acquired primary achievements are as follows(:1)It is established left-turn and through delay model of two phase intersection, according to the queuing theory and gap theory. It is obtained the critical condition of exclusive left-turn lane, exclusive left-turn phase and left-turn operation. It is easy to apply in the traffic control system; (2) It is established left-turn queueing model according to the accumulation curve principle and the traffic wave theory, and obtained the geometry, volume and signal timing critical condition of the left-turn waiting area. It is provided the theory basis for seting up th left-turn waiting area; (3)It is proposed variable traffic lane control algorithm under different condition and the pre-signal's establishment method, it is provided the new mentality for the variable traffic lane's establishment.