Study On The Real-Time Traffic Control Strategy Of Oversaturated Intersection Group On Urban Arterial

Aiming at retrieve or/and solve the traffic supply-demand contradiction of oversaturated intersection(group),based on the interrupted traffic flow charac-terristic of urban street,regarding the overflow queue on the link between intersections as the key to the contradiction,the dissertation analyses the mechanism of intersection(group)'s capacity loss resulting from overflow queue's spillback,and the law of intersection(group)'s delay augment due to the capacity loss abovementioned.Next,'reality system--mathematic model' method of systematics is applied to the modeling of the optimization control of oversaturated intersection group on arterial.The objective function of the 'non-linear planning' and 'conditional extreme value' mathematic model is "travel delay minimization of arterial",and the constraint condition thereof is "zero capacity loss of arterial(i.e.the avoidance of overflow queue's over-range spillback)".Under the precondition that the sum amount of surplus traffic on arterial (i.e.global load) remains fixed,on one hand,each and every intersection must compete against its adjacent intersections for the sake of the local goal of "load/delay minimization of single intersection(i.e.isolated intersection)",on the other hand,each and every intersection must cooperate with its adjacent intersections for the sake of the global goal of "load/delay minimization of multiple intersections(i.e.intersection group)".In view of the equality of the functional weight of each and every intersection,the "proportioned(i.e. equalized)"saturation degree,as the unification of the opposites of competition and synergy,is the feasible and the unique feasible global optimization solution.Emphasis must be placed on the fact that the lack of one-to-one mapping relations between the key variables:intersection saturation degree, overflow queue length and its time-dependent change rate,may lead to non-solution within the feasible domain subjecting to the constraint abovementioned.Therefore,as far as the realization of the equalized saturation degree is concerned,it is indispensable to force a certain number of intersections' saturation degrees to decrease less than 1.00 according to particular situation(s),in order to shorten the overflow queue length(s) aiming at the accordence with the constraint abovementioned, In contrast to the optimization solution of the mathematic model(within theoretical research category) of oversaturated intersection group,the optimization strategy of the reality system(within engineering technology category) of oversaturated intersection group,is the "synergic equalization" of the intersections' saturation degrees,based on increasing single intersections /multiple intersections' capacity(s).â—†In the forepart of strategy-applying,i.e.on condition that the oversaturation-degree of each and every intersection is higher than 1.00,the equalized saturation degree must be regulated to approach the minimum,in order to balance the traffic intensity of surplus traffic(i.e.overflow queue length's time-dependent change rate),aiming at controlling overflow queue's small-scale existence and restraining overflow queue's large-scale extension, finally,achieving the decrease of the global "equilibrium delay" and the global "stochastic delay" of arterial.â—†In the later stage of strategy-applying,i.e.on condition that the oversaturation-degree of each and every intersection is lower than 1.00,the equalized saturation degree must be regulated to approach the average,in order to alleviate the traffic density of surplus traffic(i.e.overflow queue length), achieving the decrease of the global "overflow delay" of arterial,last but not least,avoiding overflow queue's over-range spillback and guaranteeing "zero loss" of intersection capacity.Plus,in order to avoid the transfer or the expansion of oversaturation,in the course of strategy-applying anaphase,it is indispensable to increase the capacity of a certain number of undersaturated intersections located at oversaturated intersection group system(downstream direction) periphery,for the sake of----on one hand,the room for manoeuvre of balancing the traffic intensity of surplus traffic;on the other hand,the space for accommodation of alleviating the traffic density of surplus traffic.