4.3 General control of cross-ring
4.3.1 passage space design
1. Import Road Layout The purpose of the implementation of signal control is to enable different traffic flows, the separation in time. In order to facilitate the implementation of signal control, it is necessary to import Road lane divided function (see Figure 4), enables the flow of traffic各行其道to avoid mutual interference.
2. Central Road layout
Different flows in order to avoid causing traffic chaos intertwined, Central Road improve traffic capacity, as well as with the import function to match the Road driveway, it is necessary to Ring Road also divided roadway function, is mainly divided into lanes to turn left and go straight ahead (see Figure 4). Ring Road that is at least has a straight, a left turn lane.
4.3.2 Determination of signal phase
Because of the role of Bay Road, the traffic to turn left and straight on to the conflict between traffic can actually evolve into a degree of interwoven, the result of the implementation of four-way ring to pay the general control, to be used in the form of two-phase control; more Road Central, submitted by the specific circumstances of the case to determine visibility.
4.3.3 signal configuration and priority rules
1. Signal configuration based on the above analysis, the arrow lights should be configured in order to facilitate the flow of different traffic with different traffic signal.
2. Priority rule ring along with the phase because of the existence of different traffic flows, the left turn traffic flow and traffic flow straight to the potential for conflict exists between, it was necessary to set the priority rules, usually in the same phase, the straight traffic stream have precedence in the left turn traffic flow (also visible on the actual situation).
4.3.4 Signal Timing
Ring Road divided roadway function and implementation of signal control can be used to eliminate cross-Ring Road in the loop-cutting issues, thus the control method in the signal control principle with the general level-crossing control method is similar to Webster-based allocation method to determine when the timing program, and depending on the actual coordinate the flow of traffic than the actual green time. However, due to the Central Road, vehicles traveling the speed limit and driving distance is longer, according to the practice of using yellow light time of 3s may lead to the end of yellow line to turn left through the parking of vehicles with another phase of the early exit of vehicles (cars to turn left or go straight vehicles) in the Bay Road entrance of intertwined or conflicts, which have a need to re-determine the time between green and yellow light duration.
Located around the island radius r0, Ring Road, the width of each lane w, calculated traveling speed v0, the driver reaction time t0, then import Road vehicles from passing through the most lateral straight junctions adjacent most lateral point of conflict is about the shortest distance
(17)
So (two-phase case) the Green interval I for
(18)
By type (13) yellow light time can be identified.
5 Ways to control the application of the conditions of analysis
1. Flow conditions are usually, non-signal-controlled roundabout capacity value of the experience of 2 000pcu / h or so, so when the actual traffic demand roundabout approach or exceed the value of this experience that it is necessary to the implementation of signal control is proposed in this paper The three kinds of control mode, both for flows exceeded 2 000pcu / h and the control signals required to pay in terms of ring. The first two kinds of control method is more applicable to a larger left turn traffic situation.
2. Intersection turn left two-step control of the geometric conditions of the ring to pay, generally applicable to large diameter around the island, Central Road has enough space for traffic to turn left holding queue of traffic flow; turn left step in the control (not around the island) of the Central settlement, generally applies to smaller diameter around the island, around the island has enough space for laying the traffic lane to turn left into the traffic flow of space, and turn left trochoid truck lanes turning radius should be not less than diversion routes set up in accordance with the minimum requirements turning radius; the implementation of the general control of the ring to pay, the general can not satisfy the above two control methods of the geometric conditions (also unable to broaden the reach of these requirements).
6 Conclusion
Roundabout past the implementation of signal control, most of them apply the planar intersection of the control method, it is difficult to effectively adapt to the characteristics of the traffic roundabout, a reasonable solution roundabout traffic problems. In this paper, circular control mode is in the roundabout traffic characteristics and traffic problems in an in-depth study based on, and around the island for different scale, different intersections of space, give different control modes, the result of ring type intersection signal control and management of the theoretical research and practical applications are of great value. Since the study conditions, none of three kinds of models of non-motor vehicle and pedestrian interference and other possible cases, which have yet to be combined with the actual situation in a variety of further improving the