Research On Control Method Selection And Time Space Design Of Roundabout In City Roads

In the main roads of urban transportation network numerous roundabouts for the past decade are built, which have played an important role in road traffic history. However, with the rapid increasing of road traffic flows, traffic efficiency of roundabout decrease greatly, to improve its traffic capacity and make full use of its time and space resource by using the signal control on the roundabout. The signal control roundabout have been divided into two kinds by left turn control mode, the first is single signal control (only install single lamp on the entry direction of ring, taking simple two-phase control), the second is dual signal control (install single lamp on the entry direction of ring and run off direction of ring, Left turning vehicles were quadratic controlled by signal in the ring before run off the ring). Actually what conditions does the roundabout each control mode suit , as well as how big value of maximum traffic capacity can achieve each mode of control roundabout? At present not many about this aspect are researched, the paper has launched the research in light of this.First, the paper has carried on the analysis in the capability and delay of the non-signal control, the single signal control and dual signal control roundabout. The non-signal control roundabout capacity model has regression analysised based on vehicle arrival rate, compared with the gap-acceptance theory model, the new model has advantages that model can be easily calculated and parameters can be easily obtained, moreover its delay formula has inferred support from the capability achievement that based on gap-acceptance theory. In addition through the operational characteristics of vehicles at roundabout, the roundabout capacity formula of single and dual signal control has been deduced in the stop line ways Next, the paper has made the analysis to the control mode choice of roundabout from two kind of angles, one angle is capability maximization, the other angle is delay under X=0.8(saturation is 0.8) with traffic capacity ratio minization. Research indicates that the roundabout wether choose the signal control under low channelization condition shoule uses the second angle, Overall evaluation traveling capability and the delay situation makes the judgment. Regarding roundabout signal control modle choice shoule uses the fist angle, only makes the judgment from the capability maximization angle.But after, the paper has also done the corresponding research to space and time optimization design.under the roundabout each kind of control mode. Time and space design schematic diagram of typical roundabout is given, and the the design of traffic signal setting of signal roundabout is mainly analyzed. To sigle- signal control roundabout, determination method of optimal period are put forward based on its capacity characterities, to double- signal control roundabout, mainly analyzes the design of phasing-sequence, calculation of change interval and green time.Finally, the paper makes the control mode choice using the research results to the example roundabout, and has designed three kind of control mode intersection design plan. Using the VISSIM simulation confirmed the computed results The confirmation result indicated the paper research results are scientify and rationality, which provide evidence for the transformation project to roundabout.