CN101251953A - An Asymmetric Spatiotemporal Optimal Control Method for Roundabouts - Google Patents

Abstract

An asymmetric space-time optimization control method that can be used in roundabouts. At each entrance of the roundabout, there are two sets of signal lights, and these two sets of lights assign the right of way to vehicles entering the ring and vehicles inside the ring in turn, so that According to the signal light control scheme, alternately pass through the roundabout interweaving section. And according to the traffic conditions around the island, the traffic signal time for left-turn traffic flow is determined with the maximum number of parking lots as the constraint condition; in addition, the traffic signal start-up and interruption time of the horizontal intersection entrance roads all take into account the safety of traffic flow and the need for maximum traffic. Implementation of flexible control measures for an optimally coordinated use of the "spatial and spatial" resources of the roundabout. Optimal control according to dynamic changes in traffic flow. The invention can effectively alleviate the congestion and deadlock conditions of the roundabout, improve the safety of the intersection, and is easy for practical application.

Description

An Asymmetric Spatiotemporal Optimal Control Method for Roundabouts

technical field

The invention belongs to the technical field of road traffic control, in particular to a control technology capable of improving congestion at roundabouts and reducing the number of accidents at the intersections.

Background technique

Due to the simple management means of uncontrolled roundabouts, which can effectively reduce vehicle delays under low traffic conditions, reduce traffic accident rates, and optimize the environment, the utilization rate is relatively high in the early construction of various cities in my country, and it is also It solved some problems of urban traffic at that time very well and played a certain positive role.

However, with the continuous and rapid development of my country's economy, the number of motor vehicles in cities has continued to increase, and the traffic flow has also increased, exceeding the generally considered optimal traffic flow limit for uncontrolled roundabouts, that is, the traffic volume of motor vehicles is between 1000-2700pcu /h. With the increase in traffic demand, uncontrolled roundabouts have a series of problems such as traffic congestion, increased accident rate, increased vehicle delay, and increased saturation.

In the prior art, up to now, most roundabouts in the world adopt no-signal control. No signal control roundabout is affected by the weaving section, no matter how many roadways there are in each entrance road, the traffic flow with weaving must weave on the ring road, when the length of the weaving section is less than 2 times the minimum allowable weaving section length , its throughput is actually only equivalent to the throughput of one lane, so its traffic capacity can only reach the maximum theoretical value of one lane. The increase, but the increase will not be too large, so its allowable throughput will not be very high.

Therefore, when the total inflow traffic volume (excluding right-turn traffic volume) of each entrance road is low, the traffic efficiency of the roundabout can still be maintained at a high level; When there is no capacity, it will cause traffic congestion and obstruction on the ring road, and even the entire intersection will be blocked, and further cause traffic congestion at each entrance road. When there are non-motor vehicle traffic flow and mixed pedestrian traffic, its problem will be more serious.

At the same time, the uncontrolled roundabout, because its capacity is limited by the weaving area, can not effectively relieve the congestion of the intersection through the widening of the conventional intersection approach; while the approach similar to the conventional intersection Signal control also cannot effectively solve the traffic capacity bottleneck problem in the weaving area.

Contents of the invention

The main purpose of the present invention is to provide a time-space resource optimization control technology for roundabouts, which can effectively alleviate the congestion and deadlock conditions of intersection roundabouts, improve the safety of intersections, and is easy for practical application.

For achieving the above object, solution of the present invention is:

At each entrance of the roundabout and on the ring road, two sets of signal lights are set up, and these two sets of lights assign the right of way to the vehicles entering the ring and the vehicles inside the ring in turn, so that they can alternately pass through the roundabout interweaving section according to the signal light control scheme. And according to the traffic conditions around the island, the traffic signal time for left-turn traffic flow is determined with the maximum number of parking lots as the constraint condition; in addition, the traffic signal start-up and interruption time of the horizontal intersection entrance roads all take into account the safety of traffic flow and the need for maximum traffic. Implementation of flexible control measures for an optimally coordinated use of the "spatial and spatial" resources of the roundabout. Optimal control according to dynamic changes in traffic flow. To adapt to the inhomogeneity of flow in each flow direction of the traffic flow around the island and the time-varying characteristics of the traffic flow around the island, it provides multi-period signal control phase sequence optimization, and performs the best distribution of traffic flow combination, connection and green signal ratio at the intersection, reducing the average vehicle delay and balancing Saturation of traffic flow in all directions, and shorten the queue length as much as possible.

A traffic control method that can be used at roundabouts. According to traffic demand and road conditions, signal control is performed on roundabouts, and secondary stop lines are set for left-turn traffic flows; according to the comparison of flow rates and intersection entrances and ring roads Nesting and lapping of signal phases are carried out to solve the deadlock phenomenon of the roundabout when the traffic is heavy, improve the traffic performance of the roundabout, and improve traffic safety.

Further, set double stop lines at the entrance road and the ring road, both of which are under signal control.

Embed the left-rotation phase into the straight-ahead phase, and set the signal phase of two large phases and eight small phases.

The asymmetrical signal control method is used to calculate the green light start time of each entrance road according to the traffic demand and the comparison situation, and realize the close connection of the traffic flow.

First of all, the first stop line, special left-turn lane and special left-turn signal light are set on the entrance road; in addition, the second stop line is set before the conflict point between the left-turn traffic flow of each entrance road and the left-turn traffic flow of the opposite entrance road on the ring road , and equipped with corresponding special signal lights; the left-turn traffic flow will pass through the intersection after passing through the secondary traffic signal.

In order to rationally utilize the parking space of the left-turn traffic flow in the ring road, the passing signal time of the left-turn traffic flow should be determined according to the constraint condition of the maximum parking number;

The opening and closing time of the traffic signal at the horizontal intersection entrance road should consider the safety of traffic flow and the needs of maximum traffic, implement flexible control measures, and optimally coordinate the use of the "space-time" resources of the roundabout.

In order to reduce the time loss and adapt to the inhomogeneity of traffic flow in each flow direction around the island and the time-varying characteristics of the traffic flow around the island, multi-period signal control phase sequence optimization is provided, and the combination of traffic flow and the real-time green signal ratio optimization control at intersections are dynamically carried out to reduce traffic flow. delay, equalize the saturation of traffic flow in all directions, and minimize the queue length.

Aiming at the congestion phenomenon of roundabouts widely existing in Chinese cities, the invention proposes an asymmetrical space-time optimal control technology for roundabouts. Based on the ideas of space-time combination and optimization and asymmetric signal control, the optimal utilization of time-space resources (including entrance roads and ring roads) and asymmetric signal control methods of roundabouts are proposed. For congested roundabouts, this method can effectively prevent the "deadlock" of the intersection (due to the serious mutual interference of the incoming and outgoing traffic flows, the phenomenon that the traffic flow cannot enter or exit the intersection); reduce the queuing of each entrance road length and vehicle delays; and reduce the number of accidents at intersections. For non-congested roundabouts, this method can improve traffic order and greatly reduce the number of accidents at the intersection.

Description of drawings

Fig. 1 is a schematic diagram of a typical roundabout signal control basic mode and a vehicle trajectory according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of a typical roundabout signal phase setting mode according to an embodiment of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the embodiments shown in the accompanying drawings.

1. Implement two-step control on left-turn traffic flow

This law adopts a two-phase traffic signal control method for roundabout intersections, and the corresponding entrance roads, stop lines, and signal light facilities are arranged as shown in Figure-1. First of all, the first stop line, special left-turn lane and special left-turn signal light are set on the entrance road; in addition, the second stop line is set before the conflict point between the left-turn traffic flow of each entrance road and the left-turn traffic flow of the opposite entrance road on the ring road , and equipped with corresponding special signal lights. The left-turn traffic flow will pass through the intersection after passing through the secondary traffic signal (entrance traffic signal, ring road traffic signal). The layout of the first stop line, the second stop line and signal lights at the intersection and the vehicle trajectory are shown in Figure 1.

2. Coordinate and optimize the "space-time" resources of the roundabout

First of all, in order to rationally utilize the parking space of the left-turn traffic flow in the ring road, the traffic signal time of the left-turn traffic flow should be determined according to the constraint condition of the maximum parking number; in addition, the traffic signal start-up and interruption time of the transversely intersecting entrance roads should be considered To meet the needs of traffic flow safety and maximum traffic, implement flexible control measures and best coordinate the use of "space-time" resources at roundabouts. In general, the signal control of eight small phases embedded in the two large phases of the intersection is realized. For the intersection shown in Figure 1, its signal phase mode setting is shown in Figure 2. In order to reduce the time loss and adapt to the inhomogeneity of traffic flow in each flow direction around the island and the time-varying characteristics of the traffic flow around the island, multi-period signal control phase sequence optimization is provided, and the combination of traffic flow and the real-time green signal ratio optimization control at intersections are dynamically carried out to reduce traffic flow. delay, equalize the saturation of traffic flow in all directions, and minimize the queue length.

(1) Traffic space design

·Lane layout

According to the inflow traffic demand characteristics (flow rate and flow direction) and passing space conditions, at least one left-turn, one straight-going, and right-turn special lane should be set up on the entrance road; at least one left-turn and one straight-going special lane should be set up on the ring road.

·Parking line design

In order to realize the two-step control of left-turn traffic flow, stop lines must be set on the entrance road and the ring road respectively to ensure the orderly flow of traffic.

· Determination of ring capacity

a. There is only one dedicated left-turn lane on the ring road

Suppose the radius of the roundabout is r ₀ , the width of the roundabout is w, and the central angle of the triangle formed by the intersection point, the midpoint of the second stop line (on the first roundabout) and the center of the island is α (as shown in Figure-2) , The driving distance of the first car turning left before the first stop line at the i-th intersection to the intersection point A _i is d _{1, i} , and the speed limit of the ring road is v ₀ , then the queuing length l _i in the first left-turn lane is :

${\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&pi;\&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; 180</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 0.5</span>}\mathrm{<span\; class="notranslate">\; w</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.35</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}$

Therefore, the capacity of a left-turn lane on the ring road corresponding to the i-th intersection is (in pcu):

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 5</span>}}<span\; class="notranslate">\; [</span>\frac{{\mathrm{<span\; class="notranslate">\; \&pi;\&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; 180</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 0.5</span>}\mathrm{<span\; class="notranslate">\; w</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.35</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ]</span>$

b. There are n left-turn lanes on the ring road

C _n,i = nC _1,i

c. If there are m (m > 1) straight lanes on the ring road, part of the space in the through lane can be used for queuing, but at least one through lane must be reserved for the passing of through vehicles entering the ring road. Accordingly, the ring road capacity corresponding to an intersection is (unit: pcu)

C _mn,i =nC _1,i +(m-1)C _1,i -0.75m(m-1)

d. So the total capacity of the ring in one cycle is (unit: pcu)

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; mn</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}$

where r is the number of roundabouts.

(2) Signal control optimization method

·Signal light configuration

In order to optimally coordinate and control the left-turn, straight-going traffic flow on the entrance road and the left-turn traffic flow on the ring road, it is necessary to configure a signal machine with linkage control function and corresponding signal lights. The specific configuration is: set 4 sets of arrow signal lights at the position visible to vehicles in front of the first stop line to control the left turn and straight traffic flow on the entrance road; set 4 sets of signal lights at the position visible to vehicles in front of the second stop line to control traffic on the ring road left-turn traffic. See Figure-1 for details.

·Private rules

In principle, the intersection adopts two-phase signal control; if the left-turning vehicle encounters a red light before the second stop line, it will stop and wait, and the other phase will pass at the green light. There is a coordination relationship between the green light signal and the turn-on time of the green light of another phase, which needs to be determined according to the actual control requirements.

·Phase design

For the large-scale four-way ring intersection, due to the space conditions of the ring road, two-phase control is adopted at the entrance road, and the green light time of each flow direction is adjusted according to the late start and early stop mode in combination with the unbalanced flow rate of each entrance road; , the corresponding two-phase control is adopted. In the case of relatively large left-turn traffic flow, if the roundabout is removed, four-phase control is required; however, this method only needs two phases, which can greatly reduce the loss of time. This also fully illustrates the advantages of the "left turn two-step control" method.

(3) Determination of key parameters of signal control

· Determination of cycle time

Since the parking and waiting left-turning vehicles are set on the ring road, the cycle time cannot be less than the sum of the emission time of the left-turning cars on the ring road. Therefore, on the ring road, set the theoretical value t _ci of the emission time of left-turn vehicles on the ring road corresponding to the i-th entrance, then

t _ci =(c _{1, i} −6)*(1/s _c )+19.5

Where s _c is the saturation flow rate on the ring, i=1, 2,...r;

Also assume that the time required to discharge vehicles in the ring road is t _c , then

${\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; cj</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \}</span>$

Where k is the phase number of a cycle. Therefore, the signal cycle time c _c required by the traffic flow in the ring road is

c _c =t _c +∑l

Where l is the start-up loss time.

At the approach road, the signal cycle time required for straight traffic flow can be calculated according to Webster's formula:

${\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1.5</span>}\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 5</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Y</span>}}$

where L is the total lost time per cycle, $Y=\underset{i=1}{\overset{\mathrm{no}}{\mathrm{\&Sigma;}}}{\mathrm{the\; y}}_i$ , y _j is the maximum value of the through lane flow ratio of the jth phase, namely ${\mathrm{the\; y}}_i=\max \{\frac{q_j}{{\mathrm{the\; s}}_c},\frac{{q^{\&prime;}}_j}{{\mathrm{the\; s}}_c},...\},$ Therefore, the theoretical value of the cycle duration of the ring intersection is

c=max{c _e , c _c }

The actual value of the cycle time can be adjusted according to the actual flow conditions.

·Light color setting and actual green light time of ring signal

In order to avoid the information interference of the ring road control on the left-turning traffic flow at the entrance of the lower phase, and to avoid the driver's misunderstanding of the ring road signal, it is necessary to simplify the ring road signal. The left-turning vehicle in the next phase should continue to drive to the second stop line of the phase; when the circular vehicle is driving, the oncoming straight traffic flow that may conflict with the left-turning traffic flow in the current phase has already set a red light, and there will be no conflict, so , The two-phase timing of the ring road can only set the time of red light and green light, and not set the time of yellow light. Therefore, the actual green light time per cycle of the ring road is the cycle time.

The actual green light time of each phase of the ring is determined by the ratio of the maximum value of the ring capacity corresponding to each phase:

${\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; *</span>\frac{\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; mn</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; mn</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \}</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}$

where j=1,2,...k

·The connection between the ring phase and the entrance phase

Vehicles parked on the ring road must pass through the intersection before the traffic flow of the next phase, so the time difference between the green light of the ring road and the green light of the next phase is another technical key in the timing scheme. The distance between the conflict points between the left-turning traffic flows at adjacent entrances, the yellow light time, and the full red time light parameters are calculated, and implemented in a linked manner.

Referring to Figure-2, set the driving distance d ₁ from the first stop line of the entrance road to the intersection point A, the driving distance d ₂ from the intersection point A to the second stop line, and the last vehicle waiting on the upper phase ring road to the intersection point A d ₃ , and the saturated flow rate s _c passing through the intersection is known, and the speed limit of the ring road is v ₀ , then the time from the last waiting car on the ring road to the weaving point is

t _w =2d ₃ /v ₀

Therefore, the time difference between the green light of the ring road and the green light of the lower phase entrance road is

$\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}{{\mathrm{<span\; class="notranslate">\; d</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; \}</span>$

The connection time between the enthroned ring phase and the entrance road phase (wherein d′ ₃ is the travel distance from the last waiting vehicle on the ring road corresponding to the opposite entrance road to the corresponding intersection point.)

·Effective green light time of each cycle of entrance road and effective green light time of each phase

The usual time allocation method is determined according to the flow rate of each entrance, but in this scheme, since the number of left-turn vehicles allowed to park on the ring road is fixed, the maximum capacity of left-turn vehicles in each cycle is also fixed. Therefore, when determining the timing scheme, the actual inflow demand of left-turn vehicles should be considered as an important factor. When the flow of left-turning vehicles is large, the effective green light time per cycle can be determined according to the emission time of left-turning vehicles:

G＝ _cc -L

If the flow of straight traffic is large, the effective green light time can be determined according to the Webster method:

G＝c _e -L

Taking the maximum flow rate ratio of the through traffic at the entrance road of each signal phase as the ratio of the effective green light time occupied by it, based on this, the effective green light time g _j of the phase can be calculated, namely:

${\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; G</span>}<span\; class="notranslate">\; *</span>\frac{{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}{\mathrm{<span\; class="notranslate">\; Y</span>}}$

Since the green light time plays a decisive role in the traffic discharge of each flow direction, in order to improve the utilization rate and traffic efficiency of the intersection, and avoid unnecessary loss or waste of traffic space and traffic time, the mode of late start and early stop can be flexibly adopted. Make appropriate adjustments to the timing scheme to determine the actual display time of the green light signal.

·Interval time between green lights and yellow lights at entrances

Since the distance between the entrance and exit of a large-scale roundabout is larger than that of a general level intersection, if the transition time of the traffic signal phase switching is 3 seconds, it may cause the straight vehicle passing the stop line at the end of the yellow light to be separated from the other phase. The vehicle (left-turning vehicle or straight-going vehicle) that leaves at the beginning conflicts, so it is necessary to re-determine the interval between green lights and the duration of yellow lights. Set the braking time of the straight vehicle on the outermost straight lane passing the first stop line at the beginning of the yellow light (or at the end of the green light) to be t ₁ , and the left-turn lane closest to the road center line between this straight lane and the adjacent entrance road on the right The distance between the formed conflict point B and the stop line of the entrance road is x ₁ , when the straight-going vehicle passes the conflict point and the adjacent left-turning vehicle reaches the conflict point, the safe distance between the two vehicles is x ₂ , the conflict point is to The distance between the stop line of the adjacent entrance road on the right is x ₃ , and the interval time between green lights is I, then

t ₁ +(x ₁ +x ₂ )/v ₀ ≥t ₀ +2x ₃ /v ₀ +I

From the above formula, the theoretical value suitable for the green light interval time of this entrance can be calculated. The same method can be used to calculate the theoretical value suitable for the green light interval time of the other three entrance roads. The sum of the four green light interval times is taken as the green light of this intersection timing scheme. Intervals. Also assume that the duration of the yellow light is A, and for each entrance, the duration of the yellow light can be determined by I=A+R ₀ (R ₀ is the duration of full red).

The above description of the embodiments is for those of ordinary skill in the art to understand and apply the present invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described here to other embodiments without creative efforts. Therefore, the present invention is not limited to the embodiments herein, and improvements and modifications made by those skilled in the art according to the disclosure of the present invention should fall within the protection scope of the present invention.

Claims (8)

1. a traffic control method that can be used for the traffic circle is characterized in that: according to transport need and road conditions, signal controlling is carried out in the traffic circle, left turn traffic is provided with the secondary stop line; Contrast situation according to flow is carried out the nested of signal phase and is overlapped setting with crossing inlet road and circuit number, to solve the deadlock situation of traffic circle when flow is big, improves the current energy in rotary island crossing, and improves traffic safety.

2. traffic control method according to claim 1 is characterized in that: at entrance driveway and circuit two stop lines are set, all carry out signal controlling.

3. traffic control method according to claim 1 is characterized in that: left turn phase is embedded in the craspedodrome phase place, carry out the signal phase setting of eight little phase places of two big phase places.

4. traffic control method according to claim 1 is characterized in that: adopt asymmetric signal control method, calculate the green light start-up time of each entrance driveway according to traffic demand and contrast situation, and realize the close linking of wagon flow.

5. traffic control method according to claim 2 is characterized in that:

First stop line at first is set, exclusive left-turn lane and special-purpose left rotaring signal lamp on the entrance driveway; In addition, before each an entrance driveway left-turn traffic flow and subtend entrance driveway left side passes the traffic flow conflict point on circuit, second stop line is set respectively, and is equipped with corresponding special signal lamp; Left-turn traffic flow will be through passing through the crossing behind the secondary right of way signal.

6. traffic control method according to claim 3 is characterized in that:

For reasonably utilizing the left-turn traffic flow parking space in the circuit, should it be the right of way signal time that constraint condition is determined left-turn traffic flow with its maximum stop of several;

7. traffic control method according to claim 3, it is characterized in that: the right of way signal of transverse intersection entrance driveway opens the bright needs that pass through with the safety that need consider traffic flow break period and maximum, implement control measure flexibly, optimal coordination utilizes " space-time " resource of traffic circle.

8. according to arbitrary described traffic control method among the claim 1-7, it is characterized in that: for reducing the loss of time, and each flows to the unevenness and the rotary island traffic flow time varying characteristic of flow to adapt to the rotary island wagon flow, the optimization of multi-period signal controlling phase place phase sequence is provided, dynamically carry out the real-time Split Optimization control in wagon flow combination and crossing, reduce car and all incur loss through delay, balanced each saturation degree to wagon flow, and shorten queue length as far as possible.

Images