CN105489027B - A kind of downstream area signal optimizing method towards "bottleneck" - Google Patents

Abstract

The invention discloses a single-point bottleneck-oriented downstream area signal optimization method. The method is to accurately describe the time-space correlation characteristics of the traffic state of the internal nodes in the area, rationally adjust the signal timing parameters of the downstream nodes, and dissipate the bottleneck of the road section from the area level. The specific steps are as follows: establish a traffic sharing rate model, and determine the regulation and control traffic flow and control area through the set threshold; then calculate the difference of the entering and leaving flow rate under the original control scheme; calculate the total mediation of upstream and downstream input capabilities required for the initial queuing amount; distribute the total mediation amount; adjust the green-to-signal ratio of traffic flow, and finally obtain the bottleneck control plan. The method of the invention is based on the downstream flow rate of the bottleneck road section, comprehensively considers various traffic flow parameters, automatically identifies the bottleneck traffic flow and controls the bottleneck-related intersection in real time, can quickly and effectively solve the bottleneck congestion situation, and is easy to implement in engineering.

Description

A Downstream Area Signal Optimization Method Oriented to Single Point Bottleneck

technical field

The invention relates to a single-point bottleneck-oriented downstream area signal optimization method, which is used for urban traffic control and management and belongs to the field of intelligent traffic research.

Background technique

With the continuous development of urban economy and the continuous expansion of urban scale, the problem of urban road traffic congestion is becoming more and more serious, which seriously affects people's daily life and the stable development of society. How to find effective ways to control traffic congestion is an important issue in traffic engineering today. One of the research hotspots in this field.

The unbalanced temporal and spatial distribution of traffic demand in the road network will cause the queue length of individual road sections to be close to or even equal to the length of the road section, which will affect the normal release of traffic flow at upstream intersections. This road section is called "bottleneck road section", and its corresponding intersection is called "bottleneck intersection". As an important node in the urban road network, bottleneck intersections may cause "domino" and "deadlock" phenomena of urban road network congestion, resulting in serious paralysis of road network traffic and serious economic and social losses. In order to improve traffic congestion in response to such phenomena, signal optimization at bottleneck intersections is particularly important.

In view of the above current situation and problems, the present invention proposes a single-point bottleneck-oriented downstream area signal optimization method, which provides a basis for refined management and control of urban traffic.

Contents of the invention

The purpose of the present invention is to provide a downstream area signal optimization method oriented to a single point bottleneck. This method accurately describes the temporal and spatial correlation characteristics of the traffic status of internal nodes in the region, reasonably adjusts the signal timing parameters of downstream nodes, and dissipates the bottleneck of the road section from the regional level.

The single-point bottleneck-oriented downstream area signal optimization method proposed by the present invention includes three parts: bottleneck control node selection, bottleneck section adjustment amount determination, and signal parameter optimization.

The first part, bottleneck control node selection. In the present invention, the impact of downstream traffic flow on the bottleneck road section will be described by establishing an expression model of traffic flow sharing rate.

In the second part, the adjustment amount of the bottleneck section is determined. The flow rate difference is calculated based on the downstream data of the bottleneck road section, the total adjustment amount is determined by the ideal dissipation time and dissipation ratio and distributed in equal proportions to the number of paths, and finally the green signal ratio of the bottleneck phase is determined by combining the expression model of the traffic flow sharing rate.

The third part is signal parameter optimization. When the phase sequence and cycle duration of the intersection remain unchanged, the optimized green signal ratio of the bottleneck phase is sent to the downstream intersection of the bottleneck section, and the green light duration of the bottleneck phase and other phases are adjusted accordingly.

The bottleneck control method that the present invention proposes, comprises steps as follows:

c1. Establish the expression model of the traffic flow sharing rate, and determine the regulation and control of the traffic flow and the control area through the preset sharing rate threshold and saturation threshold.

c2. Determine the total adjustment amount that the downstream should undertake based on the regulation of the downstream inflow rate and outflow rate, ideal dissipation time and dissipation ratio of the traffic flow.

c3. According to the number of downstream paths, calculate the adjustment amount undertaken by each path.

c4. Combining with the section information of the traffic flow regulation, determine the green signal ratio adjustment amount of the phase corresponding to the traffic flow regulation.

c5. Detailed analysis of the plan delivery time and current cycle operation status, and form the final bottleneck control plan.

Step c1 analyzes the impact of downstream traffic flow on the bottleneck road section, and determines the bottleneck control area using the preset threshold. The detailed steps are as follows:

For the entire urban road network or control area, the set of road sections it contains can be represented by N, N={n ₁ ,n ₂ ,...,n _m }, where m is the number of road sections, and i and j respectively represent road sections n The traffic flow of _i and n _j .

The traffic flow in the urban road network can be divided into road section traffic flow and entrance turning traffic flow according to their different spatial positions. With the help of the basic concepts in graph theory, let <n _i , n _j > represent the directed connection edges between adjacent road segments n _i and n _j , then the set of turning traffic flows at all entrances in the area can be expressed as:

L={l _i,j |l _i,j =<n _i ,n _j >,i,j=1,2,...,m}

For a specific road section, its traffic load is directly derived from the entry of upstream nodes. For the road sections n _i and n _j , the share rate of downstream traffic entering to upstream traffic can be expressed as:

In the formula, I ⁱ _out is the set of all output traffic flows at the downstream intersection of traffic flow i; α _j,i is the share rate of traffic flow j on traffic flow i on the road section; q _j,i is the flow rate of traffic flow j leaving traffic flow i, and That is, the flow rate (veh/s) of the turning traffic l _i,j .

A path is formed by connecting a series of road sections before and after. If two road sections n _i and n _j belong to path k at the same time, then traffic flow l _i,j also belongs to path k. Assuming that there are K paths between traffic flow i and traffic j, the sharing rate of traffic flow j passing through path k to traffic flow i can be approximated by the following equation:

The total share rate of traffic flow j to traffic flow i is

Whether a certain traffic flow can be used as the control traffic flow of the bottleneck traffic flow depends on two factors: 1) whether the share rate between the traffic flow and the bottleneck traffic flow is greater than its threshold η _d,max ; Select whether the saturation of the traffic itself is lower than a certain threshold x _d,max . Only when the above two conditions are satisfied at the same time, the traffic flow can be used as a regulated traffic flow, and the intersection where the traffic flow is located is included in the bottleneck control area.

η _d,max and x _d,max are important parameters in the process of determining the bottleneck control area, which can be set according to empirical values, and can be set as 0.3 and 0.9 respectively in the example of the present invention.

Step c2 is calculated in detail as follows:

When implementing the bottleneck control scheme, n _s represents the bottleneck road section. If the queuing length of the bottleneck road section remains unchanged, the total traffic capacity that needs to be adjusted in the upstream and downstream should be equal to the flow rate deviation between the upstream and downstream of the bottleneck road section entering and leaving under the original scheme. which is:

In the formula: △S _d is the flow rate difference (veh/s) between downstream departure and upstream entry in the original scheme; q _s,j is the flow rate (veh/s) from the bottleneck section to the exit section n _j ; L _in ^s represents the set of upstream inbound segments of the bottleneck segment n _s ; L _out ^s represents the set of downstream exit segments of the bottleneck segment n _s .

Without considering the difference between the upstream and downstream flow rates between the upstream and downstream entry and exit in the original control scheme, in order to ensure that the bottleneck of the road section is eliminated within the ideal dissipation period T, the increase in the downstream exit flow rate should satisfy:

In the formula: L _s,max is the queue length of the road section when the bottleneck is triggered (m). Since the queue length cannot be monitored in real time, it can be approximated by the length of the road section; L _s,idea is the ideal queue length of the bottleneck road section (m); n is the bottleneck The number of lanes in the road section, l is the average vehicle length.

Under normal circumstances, the upstream input per unit time when the bottleneck is triggered must be greater than the downstream output, but under the interference of road section entrance and exit and random factors, the upstream input may also be smaller than the downstream output when the bottleneck is triggered. In this case, △S _d should be defined as 0. Therefore, in order to ensure that the bottleneck of the road section is dissipated within a specific time period T, the total adjustment amount △S of the flow rate of the upstream and downstream of the bottleneck road section per unit time, △S, is:

ΔS＝ΔS _a +max{ΔS _d ,0}

In the formula, △S is the total adjustment value (veh/s) of the incoming and outgoing flow rate under the original control scheme.

Step c3 is calculated in detail as follows:

The inbound traffic flow of the bottleneck road section may include the inflow of traffic flows from multiple paths. In order to balance the traffic load increment of different paths, this paper divides the total adjustment amount of the downstream equally based on the total number of paths.

Assuming that there are K paths downstream that affect the load of the bottleneck section, the amount of adjustment that each path should bear is:

In the formula, ΔS _down is the adjustment amount that the downstream path should bear.

The detailed steps of step c4 are as follows:

Suppose traffic flow j contains lanes, and the saturated flow rate of each lane is Q _s,j , then the green signal ratio compression amount of the phase corresponding to the traffic flow is:

In the formula, △λ _s,j is the green signal ratio adjustment amount of the phase corresponding to the traffic flow j.

Step c5 takes into account the differences in downstream signal optimization schemes, and conducts a detailed analysis of the time when the scheme is issued and the current cycle running status. The detailed steps are as follows:

The traffic flow j represents the traffic flow related to the downstream bottleneck, and its phase green signal ratio compression amount △λ _s,j , then the execution time of the bottleneck phase green light is:

g' _s,j =(λ _s,j +Δλ _s,j )C _s,j

In the formula, g' _s,j is the green light duration (s) of the phase corresponding to the traffic flow j in the bottleneck control scheme; λ _s,j is the green signal ratio of the original scheme corresponding to the phase j; C _s,j is the green signal ratio of the j traffic flow The cycle time (s) of the bottleneck control scheme corresponding to the intersection.

Δg _s,j = Δλ _s,j ·C _s,j

In the formula, Δg _s,j is the green light duration that the downstream traffic flow should have increased.

Calculate the compressible green light time of the non-bottleneck-related phase: the difference between the phase green light duration and the minimum green light duration is the maximum compressible green light duration of this phase, the expression is:

Δg' _s,j ＝g _s,j -g _s,j,min

In the formula, △g' _s,j is the amount of green light duration compression (s); g _s,j is the total green light duration (s) in the original control scheme; g _s,j,min is the minimum green light duration (s).

Case 1: If Δg _s,j ≤ △g' _s,j , then the actual adjustment amount of the bottleneck-related phase is Δg _s,j , and the non-bottleneck-related phases are allocated Δg _s,j in proportion to the number of non-bottleneck phases.

Case 2: If Δg _s,j >△g' _s,j , then the actual adjustment amount of the bottleneck-related phase is △g' _s,j , and the non-bottleneck-related phases are distributed in proportion to the number of non-bottleneck phases △g' _{s, j} .

Beneficial effects of the present invention: the present invention is based on the flow rate of the upstream and downstream of the bottleneck road section, comprehensively considers various traffic flow parameters, automatically identifies the bottleneck traffic flow and controls the bottleneck-related intersection in real time, can quickly and effectively solve the bottleneck congestion situation, and is easy for engineering implementation .

Description of drawings

Figure 1 is a flow chart of the total adjustment downstream of the bottleneck control.

Detailed ways

Below in conjunction with accompanying drawing, the present invention is elaborated, as shown in Figure 1, the method process step of the present invention is as follows:

step one

Determine the control traffic flow and control area:

In the formula, I ⁱ _out is the set of all outgoing traffic flow at the downstream intersection of traffic flow i;

α _j,i is the sharing rate of traffic flow j to traffic flow i in road section;

q _j,i is the flow rate of vehicle flow j leaving vehicle flow i, that is, the flow rate of turning vehicle flow l _i,j (veh/s).

Assume that the bottleneck road section n _s is found in the road network, the inflow contribution rate of the downstream road section n _j is 0.4, and the traffic saturation is 0.7. Since η _d,max and x _d,max are 0.3 and 0.9 respectively, the downstream section n _j meets the control requirements and can be used as a bottleneck control area, and the traffic flow j can be used as a control traffic flow.

Step 2 Calculation Calculate the difference between the entering and leaving flow rates under the original control scheme:

Calculated as follows:

ΔS＝ΔS _a +max{ΔS _d ,0}

In the formula: △S _d is the flow rate difference between downstream departure and upstream entry in the original scheme (veh/s);

q _{s, j} is the flow rate (veh/s) from the bottleneck section to the exit section ω;

L _in ^s represents the set of upstream incoming road segments of the bottleneck road segment n _s ;

L _out ^s represents the set of downstream exit sections of the bottleneck section n _s .

L _s,max is the section queue length (m) when the bottleneck is triggered;

L _s,idea is the ideal queuing length of the bottleneck section (m);

n is the number of lanes in the bottleneck section;

△S is the total adjustment of the flow rate (veh/s) in and out of the upstream and downstream of the bottleneck section;

l is the average body length (m).

Assume that the upstream flow rate is 1000 (veh/h), the downstream flow rate is 800 (veh/h), the number of bottleneck lanes is 2, and it needs to be dissipated within 0.1h. When the bottleneck is triggered, the queue length of the road section is 400m. The queue length is 300m, and the average body length is 5m, then ΔS _d =200, The total adjustment amount ΔS=600 (veh/h), that is, ΔS=0.1667 (veh/s).

Step 3 Calculation of path adjustment amount:

There are K paths downstream that affect the load of the bottleneck section, and the adjustment amount that each path should undertake is:

In the formula, ΔS _down is the adjustment amount that the downstream path should bear.

If there is only one path for the upstream and downstream, the adjustment amount undertaken by the upstream and downstream remains unchanged.

ΔS _up =ΔS=0.1667(veh/s)

Step 4 The green signal ratio adjustment amount of the relevant phase:

Suppose traffic flow j contains lanes, and the saturated flow rate of each lane is Q _s,j , then the green signal ratio compression amount of the phase corresponding to the traffic flow is:

In the formula, △λ _s,j is the green signal ratio adjustment amount of the phase corresponding to the traffic flow j.

If there are two lanes downstream, and the saturated flow rate of each lane is 1000 (veh/h), then according to the above assumptions, the increase of the downstream green signal ratio is

Step 6: Node signal control scheme optimization:

Optimization of downstream intersection signal scheme

g' _s,j =(λ _s,j +Δλ _s,j )C _s,j

Δg _s,j = Δλ _s,j ·C _s,j

Δg' _s,j ＝g _s,j -g _s,j,min

In the formula, g' _s,j is the green light duration (s) of the phase corresponding to the traffic flow j in the bottleneck control scheme;

λ _s,j is the green signal ratio of the original scheme corresponding to the phase of j traffic flow;

C _s,j is the cycle time (s) of the bottleneck control scheme at the intersection corresponding to the j traffic flow;

Δg _s,j is the length of the green light that should have been increased by the downstream traffic flow;

Δg _s,j is the green light duration that the downstream traffic flow should have increased.

If Δg _s,j ≤△g' _s,j , then the actual adjustment amount of the bottleneck-related phase is Δg _s,j , and the non-bottleneck-related phases are distributed in proportion to the number of non-bottleneck phases Δg _s,j .

If Δg _s,j >△g' _s,j , the actual adjustment amount of the bottleneck-related phase is △g' _s,j , and the non-bottleneck-related phases are distributed in proportion to the number of non-bottleneck phases △g' _s,j .

The above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention. Substantial equivalent changes or modifications shall fall within the protection scope of the present invention.

Claims (6)

1. The downstream area signal optimization method facing the single-point bottleneck is characterized by comprising the following steps of:

c1, establishing a traffic flow sharing rate expression model, and determining a regulated traffic flow and control area through a preset sharing rate threshold and a saturation threshold;

c2, determining the total adjustment amount to be borne by the downstream by taking the downstream driving-in flow rate and the downstream driving-out flow rate of the regulated traffic flow, the ideal dissipation time and the dissipation proportion as references;

c3, calculating the adjustment amount born by each path according to the number of the downstream paths;

c4, determining the green signal ratio regulating quantity of the phase corresponding to the regulated traffic flow by combining the information of the regulated traffic flow section;

c5, forming a final bottleneck control scheme according to the scheme issuing time and the current cycle running state:

case 1: if Δ g _s,j ≤Δg’ _s,j Then the actual adjustment amount of the bottleneck related phase is Δ g _s,j The non-bottleneck related phase is distributed with deltag in equal proportion according to the number of the non-bottleneck phases _s,j ；

Case 2: if Δ g _s,j >Δg’ _s,j Then the actual amount of adjustment for the bottleneck related phase is Δ g' _s,j The non-bottleneck related phase is in equal proportion to the number of the non-bottleneck phaseDistribute Δ g' _s,j ；

In the formula,. DELTA.g _s,j Duration of green light, Δ g ', which should be added for the downstream traffic flow' _s,j The amount of compression is green duration.

2. The single-point bottleneck-oriented downstream area signal optimization method according to claim 1, wherein the step c1 is to analyze the influence of a downstream traffic flow on a bottleneck road section, and determine a bottleneck control area by using a preset threshold, and comprises the following detailed steps:

for the whole city road network or control area, the contained road segment set can be represented by N, N = { N = ₁ ,n ₂ ,…,n _m Where m is the number of road segments, i and j represent road segments n, respectively _i And n _j The traffic flow of (1);

the traffic flow in the urban road network is divided into two types of road traffic flow and inlet road steering traffic flow according to different spatial positions of the traffic flow; order to<n _i ,n _j &gt represents adjacent road section n _i And n _j With a directed connecting edge in between, the set of all inlet lane turn flows in the area can be represented as:

L＝{l _i,j |l _i,j ＝<n _i ,n _j >,i,j＝1,2,…,m}

for the road sections ni and n _j In other words, the sharing rate of the downstream traffic flow entering the upstream traffic flow can be expressed as:

in the formula I ⁱ _out The set of all output traffic flows at the downstream intersection of the traffic flow i; alpha is alpha _j,i The sharing rate of the traffic flow j to the traffic flow i in the road section is set; q. q.s _j,i The flow rate of the outgoing flow i for the flow j, i.e. the diverted flow l _i,j The flow rate of (c);

the route is formed by connecting a series of road sections, if two road sections n are connected _i And n _j While belonging to path k, then traffic flow l _i,j Also belong to path k(ii) a Assuming that K paths coexist between the traffic flow i and the traffic flow j, the sharing rate of the traffic flow i by the traffic flow j through the path K can be estimated approximately by the following formula:

the total share rate of the traffic flow j to the traffic flow i is

Whether a certain traffic flow can be used as the regulated traffic flow of the traffic flow on the bottleneck road section depends on two factors: 1) Whether the sharing rate between the traffic flow and the bottleneck traffic flow is greater than a threshold eta _d,max (ii) a 2) Aiming at downstream 'leakage' traffic flow, whether the saturation of the traffic flow to be selected is lower than a certain threshold value x or not _d,max (ii) a When the two conditions are satisfied at the same time, that is, the sharing rate between the traffic flow and the bottleneck traffic flow is greater than the threshold eta _d,max And aiming at the downstream 'leakage flow' traffic flow, the saturation of the traffic flow to be selected is lower than a certain threshold value x _d,max (ii) a The traffic flow direction can be used for regulating the traffic flow, and an intersection where the traffic flow is located is brought into a bottleneck control area;

η _d,max and x _d,max The method is an important parameter in the bottleneck control area determining process and is preset according to the actual situation.

3. The single-point bottleneck oriented downstream area signal optimization method according to claim 1, wherein the step c2 is specifically as follows:

with n _s Representing a bottleneck section, if the queuing length of the bottleneck section is kept unchanged, the total traffic capacity needing to be adjusted at the upstream and the downstream should be equal to the flow rate deviation between the upstream and the downstream driving-in and driving-out of the bottleneck section under the original scheme, namely:

in the formula: delta S _d The difference value of the downstream driving-off flow rate and the upstream driving-in flow rate in the original scheme is obtained; q. q.s _s,j From the bottleneck section into the exit section n _j The flow rate of (c); l is _in ^s Representing a bottleneck section n _s The upstream drive-in road segment set; l is _out ^s Representing a bottleneck section n _s A set of downstream exit segments;

under the premise of not considering the difference value between the upstream and downstream driving-in flow rate and the driving-out flow rate in the original control scheme, in order to ensure that the bottleneck of the road section is eliminated in the ideal elimination time period T, the downstream driving-out flow rate increment is satisfied:

in the formula: l is a radical of an alcohol _s,max The method is the road section queuing length when the bottleneck is triggered, and can be approximately replaced by the road section length because the queuing length cannot be monitored in real time; l is _s,idea The queuing leader is an ideal queuing leader for the bottleneck road section; n is the number of lanes on the bottleneck section, and l is the average vehicle body length;

normally, the upstream input per unit time is necessarily greater than the downstream output when the bottleneck triggers, but the upstream input may be smaller than the downstream output when the bottleneck triggers under the interference of the road section entrance and exit and random factors, and Δ S should be defined at this time _d Equal to 0; therefore, to ensure that the bottleneck of the road section is dispersed in a specific time period T, the total adjustment quantity Δ S of the incoming and outgoing flow rates of the upstream and downstream road sections of the bottleneck in a unit time is as follows:

ΔS＝ΔS _a +max{ΔS _d ,0}

in the formula, Δ S is the total adjustment amount of the driving-in and driving-out flow rate under the original control scheme.

4. The single-point bottleneck-oriented downstream area signal optimization method according to claim 3, wherein the step c3 is specifically as follows:

and (3) equally dividing the total downstream regulating quantity by taking the total number of the paths as a reference, and assuming that K paths exist in the downstream influencing the load degree of the bottleneck road section respectively, the regulating quantity born by each path is as follows:

in the formula,. DELTA.S _down The amount of adjustment to be undertaken by the downstream path.

5. The single-point bottleneck-oriented downstream area signal optimization method according to claim 4, wherein the step c4 is specifically as follows:

suppose that flow j containsEach lane has a saturation flow rate of Q _s,j Then, the green ratio compression amount of the phase corresponding to the traffic flow is:

in the formula, Δ λ _s,j The green ratio adjustment amount of the phase corresponding to the traffic stream j.

6. The single-point bottleneck oriented downstream area signal optimization method according to claim 5, wherein the step c5 is specifically as follows:

the traffic j represents the traffic related to the downstream bottleneck, and the compression amount of the phase green ratio is delta lambda _s,j Then, the execution time of the bottleneck phase green light is:

g' _s,j ＝(λ _s,j +Δλ _s,j )C _s,j

in formula (II), g' _s,j In the bottleneck control scheme, the green light duration(s) of the phase corresponding to the traffic stream j; lambda [ alpha ] _s,j The green ratio of the original scheme of the phase corresponding to j; c _s,j The bottleneck control scheme period(s) of the intersection corresponding to the j traffic flow is long;

Δg _s,j ＝Δλ _s,j ·C _s,j

in the formula,. DELTA.g _s,j Green time period that should be added for downstream traffic;

calculating compressible green time of non-bottleneck related phase: the phase green light duration and the minimum green light duration difference is the maximum compressible green light duration of the phase, and the expression is as follows:

Δg' _s,j ＝g _s,j -g _s,j,min

in the formula,. Delta.g' _s,j Green light duration compression; g _s,j The total duration of the green light is the original control scheme; g _s,j,min Is the minimum green light duration;

case 1: if Δ g _s,j ≤Δg’ _s,j Then the actual adjustment amount of the bottleneck related phase is Δ g _s,j The non-bottleneck related phase is distributed with deltag in equal proportion according to the number of the non-bottleneck phases _s,j ；

Case 2: if Δ g _s,j >Δg’ _s,j Then the actual amount of adjustment for the bottleneck related phase is Δ g' _s,j The non-bottleneck related phase is distributed by delta g 'according to equal proportion of the non-bottleneck phase number' _s,j 。