CN105913666A - Optimized layout method for variable speed limit signs on expressway mainline - Google Patents

Abstract

The invention discloses an optimized layout method for variable speed limit signs on an expressway mainline. The optimized layout method comprises the following steps: identifying a hazardous bottleneck road section on an expressway based on an accident risk forecasting model, then determining the length of a variable speed limit control road section according to threshold value setting, setting various variable speed limit sign layout density schemes, solving an optimal control strategy for each scheme, and performing investment-benefit analysis aiming at different schemes to determine an optimal speed limit sign layout scheme. According to the optimized layout method, the shortcoming that no theoretical support is provided for variable speed limit sign layout in the conventional research is overcome; the length of the variable speed limit control road section and the speed limit sign layout density are determined according to a traffic safety improvement effect and an investment-benefit ratio, so that a variable speed limit control concept and the strategy can achieve the best benefit.

Description

A kind of through street main line variable speed-limit sign optimizes distribution method

Technical field

The invention belongs to traffic analysis technical field, be specifically related to a kind of through street main line variable speed-limit sign optimization and lay Method.

Background technology

Variable speed-limit control technology is according to traffic flow detector acquisition real-time traffic stream information on through street main line, by changing Conjugate the speed limit that the variable speed-limit sign in trackside is issued, thus traffic flow is run and carries out actively regulating.Along with more coming The most through streets use variable speed-limit to control in this dynamic traffic control strategy variable speed-limit control system, variable limit The analysis that variable speed-limit using effect is affected by the installation position of speed mark becomes ever more important.

Previous scholars is studied for through street Traffic flow detecting implantation of device scheme, and result shows to work as Traffic flow detecting The laying spacing of equipment reaches 0.47 miles per hour, and real-time accident risk prediction model based on traffic flow data can reach relatively Good precision of prediction.But, research not yet lays problem for variable speed-limit sign on through street in the past and conducts a research. In the past in research, variable speed-limit sign is the most consistent with Traffic flow detecting implantation of device, in each Traffic flow detecting equipment position Install variable speed-limit sign.In research, variable speed-limit sign laid spacing in the past is 0.31 mile to 0.5 mile, actual In the variable speed-limit system of application, mark lays spacing is 0.5 mile to 3 miles.In the past variable speed-limit sign generally according to Research worker subjective desire and arrange, lack theoretical and technical support, it is impossible to guarantee that layout scheme is system optimal.This Bright proposition improves the through street main line variable speed-limit sign optimization of effect analysis and analysis of Investment Benefit based on traffic safety Distribution method, compared to existing variable speed-limit sign distribution method more scientific and effective, can give full play to variable speed-limit control Effect, be prone to decision-making simultaneously.

Summary of the invention

The problem to be solved in the present invention is: variable speed-limit sign was arranged generally according to research worker subjective desire in the past, Lack theoretical and technical support, it is impossible to guarantee that layout scheme is system optimal.The present invention proposes one and changes based on traffic safety The through street main line variable speed-limit sign of kind effect analysis and analysis of Investment Benefit optimizes distribution method, according to different accidents Risk threshold value determines corresponding hazardous road length, and foundation traffic safety improves effect and optimum is taked in Cost-benefit analysis Layout scheme.Before overcoming, variable speed-limit sign layout scheme relies on the theoretical defects of subjective judgment with not enough.

Technical solution of the present invention is:

The present invention proposes a kind of scientific and reasonable through street main line variable speed-limit and controls lower this mark cloth of variable speed-limit traffic If the optimization method of scheme, based on accident risk prediction model, it is contemplated that hazardous road length under different risk threshold values and The traffic safety of different layout schemes improves effect and cost-benefit ratio, to scientific and reasonable laying variable speed-limit sign tool Significant, overcome the deficiency that in conventional variable speed-limit sign the procedures of establishment, random big subjectivity is strong.Example shows, The method to set up that the present invention proposes has good effect, is better than conventional method to set up.

Accompanying drawing explanation

Fig. 1 is that variable speed-limit sign of the present invention optimizes distribution method flow process.

Fig. 2 is section Loop detector layout schematic diagram.

Fig. 3 be the present invention section in rear-end collision risk domain distribution schematic diagram.

Fig. 4 be the present invention different accident risk threshold values under Dangerous Area length schematic diagram.

Fig. 5 is the layout scheme method for optimizing figure of the present invention

Fig. 6 is each section accident risk spatial distribution curve in example.

Fig. 7 is different layout scheme safe effects in example.

Fig. 8 is different schemes cost-benefit ratio in example.

Fig. 9 is the layout scheme method for optimizing figure in example.

Detailed description of the invention

The present invention is based on accident risk prediction model, it is contemplated that the hazardous road length under different risk threshold values, different cloth If the traffic safety of scheme improves effect and cost-benefit ratio, establish through street main line variable speed-limit sign and optimize cloth Equipment, method.Variable speed-limit controls mark optimization distribution method flow process and refers to Fig. 1.

The first step is periodically to gather the traffic flow of through street, traffic density and the speed that many groups use variable speed-limit to control Degrees of data, as shown in Figure 2.Concrete grammar is, arranges inductive circular loop detector recording at a certain pile No. of through street By each car of detector location by the information such as time, travel speed, time headway and Vehicle length, time span Variable speed-limit control time need to be comprised and without variable speed-limit control time simultaneously.The every 5 minutes information to being collected is divided Variable speed-limit value carries out integrated respectively obtaining this traffic flow at this pile No. under different speed limits and density in 5 minutes, Record current time, weather conditions and variable speed-limit controlled state simultaneously.If being in non-variable Control for Speed Limitation state, remember For NVSL, if being in variable speed-limit controlled state, record current speed limit.Weather is chosen from this raw data base (without misty rain) in good condition, visual condition good (non-night), the data of road geometrical condition good (non-interwoven district), Whether selected data are in the data under variable speed-limit controls according to it and different speed limits is sorted out, To the basic data analyzed for accident risk.

Second step is based on traffic flow basic data, uses street accidents risks forecast model to vehicle accident wind in each section Danger calculates.Can weigh with following formula for its accident risk of rear-end collision.

$Logit\left(P\right(Y=1\left)\right)=log\frac{P(Y=1)}{1-P(Y=1)}={\mathrm{\β}}_0+{\mathrm{\β}}_1\·RCRI+{\mathrm{\β}}_2\·\mathrm{\σ}\left(O_U\right)+{\mathrm{\β}}_3\·\mathrm{\σ}\left(O_D\right)---\left(2\right)$

$RCRI=\frac{\[{\stackrel{\‾}{V}}_U(t-\mathrm{\Δ}T,t)-{\stackrel{\‾}{V}}_D(t-\mathrm{\Δ}T,t)\]\·{\stackrel{\‾}{O}}_U(t-\mathrm{\Δ}T,t)}{1-{\stackrel{\‾}{O}}_U(t-\mathrm{\Δ}T,t)}---\left(3\right)$

${\stackrel{\‾}{V}}_U(t-\mathrm{\Δ}T,t)=\underset{m=1}{\overset{M}{\Σ}}\underset{j=1}{\overset{J}{\Σ}}{V}_U^m(t_j-\mathrm{\Δ}t,t_j)/M\·J---\left(4\right)$

${\stackrel{\‾}{V}}_D(t-\mathrm{\Δ}T,t)=\underset{m=1}{\overset{M}{\Σ}}\underset{j=1}{\overset{J}{\Σ}}{V}_D^m(t_j-\mathrm{\Δ}t,t_j)/M\·J---\left(5\right)$

${\stackrel{\‾}{O}}_U(t-\mathrm{\Δ}T,t)=\underset{m=1}{\overset{M}{\Σ}}\underset{j=1}{\overset{J}{\Σ}}{O}_U^m(t_j-\mathrm{\Δ}t,t_j)/M\·J---\left(6\right)$

$\mathrm{\σ}\left(O_U\right)=\sqrt{\frac{1}{M\·J}\underset{m=1}{\overset{M}{\Σ}}\underset{j=1}{\overset{J}{\Σ}}{\[O_U^m(t_j-\mathrm{\Δ}t,t_j)-{\stackrel{\‾}{O}}_U(t-\mathrm{\Δ}T,t)\]}^2}---\left(7\right)$

$\mathrm{\σ}\left(O_D\right)=\sqrt{\frac{1}{M\·J}\underset{m=1}{\overset{M}{\Σ}}\underset{j=1}{\overset{J}{\Σ}}{\[O_D^m(t_j-\mathrm{\Δ}t,t_j)-{\stackrel{\‾}{O}}_D(t-\mathrm{\Δ}T,t)\]}^2}---\left(8\right)$

In formula, P (Y=1) is rear-end collision probability of happening,The fastest for upstream detector position in time Δ T Degree,For downstream detector position average speed,For upstream detector position average occupancy,For track, upstream detector position m average speed in jth time Δ t,For detected downstream Track, device position m average speed,For track, upstream detector position m average occupancy, J is one Collection meter traffic flow data number (J=Δ T/ Δ t, Δ t=30s) in time period, M is section section number of track-lines, and σ (OU) is upstream inspection Surveying occupation rate standard deviation, σ (OD) is downstream detector occupation rate standard deviation, and β 0, β 1, β 2, β 3 is variation coefficient.

Moving average method is used to obtain section accident risk spatial distribution, as shown in Figure 3 according to each section of street accidents risks. According to different accident risk threshold values, spatial distribution curve determines corresponding Dangerous Area length, as shown in Figure 4.

3rd step is to be set the installation position of variable speed-limit sign with laying spacing in controlling road section length, and Multiple variable speed-limit sign layout scheme is designed on the basis of this.

4th step is the variable speed-limit under every kind of speed(-)limit sign layout scheme to be controlled effect carry out simulation analysis and use excellent Change algorithm variable speed-limit control strategy and effect under every kind of layout scheme are optimized.In the specific implementation in view of short-term In emulation, traffic flow runs and cannot represent common situation in section, therefore arranges different power for accident risk in each section Weight, the accident risk curve making emulation obtain is consistent with calculating curve obtained.Use genetic algorithm to variable speed-limit controlling party Case is optimized, and first obtains research section internal detector real-time traffic flow data, calculates each road according to accident prediction model Real-time rear-end collision risk in section, starts variable speed-limit and controls, progressively by speed limit when certain section accident risk exceedes threshold value Value adjusts to desired value, arranges speed limit consecutive variations spatially, it is to avoid larger fluctuation occurs in adjacent segments speed simultaneously. When in section, accident risk is less than threshold value, variable speed-limit value progressively returns to default value.

5th step is to be analyzed each variable speed-limit sign layout scheme cost-benefit ratio respectively.Wherein income is at this Reducing accident risk ratio by variable speed-limit under layout scheme, cost is the variable speed-limit sign quantity laid, the two Ratio is program cost-effectiveness, and its computing formula is:

$R_{B-C}\left(i\right)=\frac{E\left(i\right)}{N\left(i\right)}---\left(9\right)$

Wherein,

R_B-CThe income of expression scheme i-cost ratio；

E (i) represents that in scheme i, variable speed-limit reduces accident risk ratio；

N (i) is expressed as variable speed-limit sign number in scheme i.

6th step is to determine variable speed-limit sign optimal location scheme.Based on the different schemes in the 4th step to traffic safety Improve the corresponding cost-effectiveness of each scheme in effect and the 5th step, draw layout scheme and preferably scheme, as shown in Figure 5.Fall into In figure, diagonal upper-side area is not suggested design, fall into underside area in figure for suggested design, the most not side of recommendation Case is divided into less suggested design and strong not suggested design, it is recommended that scheme is divided into relatively suggested design and strong preference scheme.? Optimal decision is carried out eventually according to different schemes present position in the drawings.

Below in conjunction with the accompanying drawings the laying optimization method of invention is carried out presented example:

Assume, as a example by 30 kilometers of sections of certain highway, in section, to comprise multiple traffic bottlenecks, peak period jam Generally occur.Research is laid with the Traffic flow detecting device of perfect in shape and function in section, lay spacing be 0.2 mile to 0.64 English In, average spacing of laying is 0.5 mile.According to research in the past, in this section, Traffic flow detecting device layout density can be expired The required precision of accident risk forecast model time full.In order to determine dangerous traffic bottlenecks section, the present invention acquires research The traffic flow data of week age in all detector location in section.According to for often sending out the reality that the bottleneck road that blocks up is set up Time rear-end collision risk forecast model, rear-end collision risk in each section is calculated, and draws accident risk space and divide Cloth curve, as shown in Figure 6.It can be seen that the street accidents risks of zones of different exists bigger in research section Difference, in figure, in the range of dotted line frame, street accidents risks is higher, as shown in Figure 6, therefore selects this region as dangerous bottle Neck section carries out variable speed-limit control, and road section scope is pile No. 14 miles to 28 miles.

Section is controlled under the different accident risk threshold value of table 1

Three kinds of accident risk threshold values are set, variable speed-limit are controlled road section length and is determined, as shown in table 1.Work as threshold value When being set to 0.053, as shown in TH1 in Fig. 6, it is shorter that variable speed-limit controls road section length, only 2.2 miles；When When threshold value is set to 0.048, as shown in TH2 in Fig. 6, variable speed-limit control area comprises two and separates section, controls Region overall length is 7.3 miles；When threshold value is set to 0.043, as shown in TH3 in Fig. 6, variable speed-limit control area For section continuous between pile No. 14.8 miles to 26.5 miles, a length of 11.7 miles.Under every kind of threshold condition, set respectively Having put three kinds of different speed(-)limit sign layout schemes, under every kind of scheme, speed limit traffic sign placement information is as shown in table 2.Such as, side Being provided with 5 speed(-)limit signs in case A1, average headway is 0.4 mile, and mark installation position is also given in table.Its Speed(-)limit sign layout density maximum (spacing is minimum) in middle option A 1, in option b 3 and C3 layout density minimum ( Away from maximum).

The different variable speed-limit sign layout scheme of table 2

Variable speed-limit under every kind of scheme being controlled effect and carries out simulation analysis, simulation time is 3 hours.Imitate in view of short-term Middle traffic flow runs and cannot represent common situation in section, therefore arranges different weight for accident risk in each section, The accident risk curve making emulation obtain is consistent with Fig. 6.Use existing variable speed-limit control strategy and optimization method pair The optimal control results of each scheme calculates, and result is as shown in table 3.

Optimal control policy and control effect under table 3 different schemes

Safe effect under different speed(-)limit sign layout schemes is as it is shown in fig. 7, result shows that in scheme C2, variable speed-limit controls Improve traffic safety effect best, reduce street accidents risks and reach 69.16%, scheme C1 and B1 control effect also Preferably, in option A 3, variable speed-limit control effect is worst, reduces street accidents risks only 5.19%.Different schemes Investment-performance analysis result is as shown in Figure 8, it can be seen that scheme C2 has the highest income-cost ratio, shows this side Under case, unit speed(-)limit sign makes accident risk decline maximum, and in scheme C3 and A2, income-cost ratio is the highest.Although side In case C1, accident risk declines maximum, but due in scheme variable speed-limit sign quantity most, therefore its income-cost ratio In all schemes minimum.

Safe effect and the cost-effectiveness of different schemes are drawn in Scheme Optimum Seeking Methods figure, as shown in Figure 9.From figure Can intuitively find out, within only scheme C2 is positioned at strong preference scope, show that scheme C2 is under limited cost puts into Achieve and control effect satisfactorily.According to result in figure, scheme C2 is optimal variable speed-limit sign in research section Layout scheme, it is recommended that apply in actual through street variable speed-limit controls.

Claims (3)

1. through street main line variable speed-limit sign optimizes a distribution method, it is characterized in that including step:

1) gathering the traffic flow data of through street Traffic flow detecting device position, step includes:

101) acquisition testing device position real-time traffic data；

102) acquisition testing device position real-time density data；

103) acquisition testing device position real-time speed data.

2) according to step 1) in the basic traffic flow data of gained, use real-time traffic accident risk prediction model to each section Interior street accidents risks calculates；Through street main line is divided into multiple section, according to detector position, two ends, each section The traffic flow data put, calculates the street accidents risks value in each section, uses the drafting of rolling average method whole quickly The spatial distribution curve of accident risk on road main line；

3) based on step 2) in the spatial distribution curve of accident risk on the through street main line that obtains, and then determine danger Road section length.By arranging risk threshold value on accident risk curve, dangerous bottleneck road can be identified, if In certain section, accident risk is higher than setting threshold value, then it is assumed that this section belongs to Dangerous Area scope；If accident risk is less than Threshold value, then show that this section is safe road section scope；

4) based on step 3) determined by need to carry out the multiple variable speed-limit of Dangerous Area Design of length of variable speed-limit control Flag control arrangements, by simulation analysis and use optimized algorithm to enter variable speed-limit strategy and effect under different layout schemes Row optimizes；

5) different variable speed-limit sign layout schemes are invested-performance analysis, set according to the position of traffic detector Different variable speed-limit sign layout schemes, and calculate corresponding income-cost ratio, its computing formula is:

$R_{B-C}\left(i\right)=\frac{E\left(i\right)}{N\left(i\right)}---\left(1\right)$

Wherein,

R_B-CThe income of expression scheme i-cost ratio；

E (i) represents that in scheme i, variable speed-limit reduces accident risk ratio；

N (i) is expressed as variable speed-limit sign number in scheme i；

6) according to step 4) in the variable speed-limit of each scheme that obtains control effect and step 5) in each scheme income-one-tenth This ratio, determines optimum variable speed-limit sign layout scheme.Respectively with scheme income and cost of investment for transverse and longitudinal coordinate, permissible Plane is divided into four quadrants, and upper right side is first quartile, be counterclockwise followed successively by two, three, four-quadrant, wherein Second quadrant is not for strongly to recommend region, and fourth quadrant is strong preference region, meanwhile, straight line y=x by first and third as Limit be respectively divided into two parts, the top half of first quartile and third quadrant is less recommends region, first quartile and The latter half of third quadrant is compares recommendation region, can obtain variable speed-limit sign according to above-mentioned steps and lay optimal case System of selection guidance diagram.The cost of investment corresponding by each scheme and scheme income may determine that each scheme is in guidance diagram Position, carries out decision-making according to the recommendation degree of this position affiliated area.

A kind of through street main line variable speed-limit sign the most according to claim 1 optimizes distribution method, its feature Described step 3) in Dangerous Area length determine during, first pass through and accurate accident risk threshold value be set to absolutely The start-stop scope of Dangerous Area is determined, secondly in view of driver close to changing driving row during Dangerous Area in advance For, it is therefore desirable to rationally extend and optimize the Dangerous Area length that variable speed-limit controls.

A kind of through street main line variable speed-limit sign the most according to claim 1 optimizes distribution method, its feature Described step 4) in variable speed-limit sign installation position in, be generally laid at Traffic flow detecting device, now speed limit mark Will quantity is equal to section internal detector quantity；The layout density of variable speed-limit sign may be lower than detector density, such as two inspections Survey the corresponding variable speed-limit sign of device.