CN100492434C - Traffic flow state analysis required detection vehicle sampling quantity obtaining method - Google Patents

Abstract

This invention relates to an obtaining method for sampling volume of detection cars needed by analyzing traffic flow state including: 1, pre-processing data of a GPS detection car, 2, matching the car with a GIS map, 3, obtaining mean velocity of highway sections, 4, obtaining sampling volume of a road net detection car, which traces vehicles to eliminated interference data, applies a nearest method to match maps then uses a space time curvature fitting model to get a mean velocity of directional sections, calculates historical data of the GPS detection car, its mean number of weight and empty in each time section network of a day, applies a sampling formula to compute the sample frequency of each time section and get the sample volume of the detection car of the road network finally.

Description

The acquisition methods of traffic flow state analysis required detection vehicle sampling quantity

Technical field

What the present invention relates to is the method for information processing in a kind of technical field of traffic transportation, specifically is a kind of acquisition methods of traffic flow state analysis required detection vehicle sampling quantity.

Background technology

Along with the development of intelligent transport technology, the dynamic estimation of urban traffic flow has been subjected to paying close attention to all the more widely.And traffic behavior estimates to be unable to do without transport information accurately and reliably, and the precision that therefore detects information approach has determined the accuracy that traffic behavior is estimated.City road network traffic flow detection information approach has multiple, mainly contains magnetic inductive coil detection method frequently, Video Detection method etc.These researchs have obtained success in some aspects and have had its practical value, but have limitation in the calculating of city road network traffic flow speed.The inductive coil monitor can obtain multiple traffic flow parameter, lays the inductive coil difficulty greatly, acquires the cost of equipment height, and is subjected to serviceable life the artificial destruction factor affecting big.Video Detection is had relatively high expectations to hardware device, is subjected to weather effect big.Use the information detecting method of Global Positioning System (GPS) (GPS (Global Positioning System (GPS))), by moving vehicle is monitored in real time, vehicle locating information such as dynamic acquisition time, position, speed, has the precision height, data volume is big, widely distributed in the city scope, be subjected to advantages such as weather effect is little, be to obtain the effective method of Real-time Traffic Information at present.Therefore the scholar puts into GPS (Global Positioning System (GPS)) probe vehicles data and carries out in the research that traffic flow modes analyzes more and more, and has obtained developing fast.Yet the probe vehicles that actually needs much samples can accurately be carried out traffic behavior and be estimated it is the problem of current primary solution.

In recent years, a lot of in the world scholars attempt calculating road-section average speed and journey time with GPS (Global Positioning System (GPS)) probe vehicles information, at this problem of probe vehicles (being detection vehicle sampling quantity) of the much samples of needs, have carried out a large amount of research.Wherein representational is that Quiroga in 1998 and Bullock deliver in " Determination of sample sizes for travel time studies " literary composition the standard variance model that obtains detection vehicle sampling quantity of proposition at " Institute of Transportation Engineers " periodical the 68th volume the 8th phase 92-98 page or leaf.This model is 1-α by introducing a fiducial interval, and degree of freedom is that the t of n-1 distributes the standard variance s of sample speed and self-defining velocity error ε _α, obtain minimum probe vehicles number.Using this model obtains and can effectively obtain detection vehicle sampling quantity.In " Determining the number of probe vehicles forfreeway travel time estimation using microscopic simulation " literary composition that Chen in 2000 and Chien deliver in " TransportationResearch Board " the 79th annual meeting, the standard variance model is improved, introduced relative velocity error ε _γAnd the road-section average speed x that n probe vehicles calculated obtains accurate more detection vehicle sampling quantity.These two kinds of models have obtained using widely in sampling quantity is estimated owing to can effectively obtain detection vehicle sampling quantity in recent years.Yet since two kinds of models all suppose in the highway section vehicle all Normal Distribution travel, this is impossible in the real road traffic; Because the standard variance s of sample speed need be calculated by n, cause model equation not seal and separate in addition, must carry out iterative, this has also increased the complex nature of the problem in the practical application.

Find by prior art documents, Singapore scholar Cheu and Lee in 2002 in " Vehicle Population and Sample Size for Arterial Speed Estimation " (detection vehicle sampling quantity that the major trunk roads velocity estimation is required) literary composition that " Computer-Aided Civil and Infrastructure Engineering " the 17th phase of periodical 53-60 page or leaf is delivered, a kind of model that obtains detection vehicle sampling quantity has been proposed.This model both kept the advantage of standard variance model, the most important thing is to overcome the deficiency that the standard variance model needs iterative.Simultaneously Cheu proposes will guarantee that the absolute error of the road network average velocity that calculates is lower than 95% (or less than 5.0km/h), the quantity of GPS (Global Positioning System (GPS)) probe vehicles must greatly facilitate actual control of traffic and road greater than 10 conclusion on every highway section.Yet Cheu does not consider GPS (Global Positioning System (GPS)) empty and load information and sends cycle differentiation that this has had a strong impact on the accuracy of result of calculation.In addition,, cause to obtain detection vehicle sampling quantity fast and accurately, restricted the popularization of method to a great extent owing to do not propose detailed analytic expression.

Summary of the invention

The objective of the invention is at above-mentioned deficiency and actual needs, propose a kind of acquisition methods of traffic flow state analysis required detection vehicle sampling quantity.The present invention has overcome prior art effectively needs a large amount of priori, complicated problems such as information, has advantages such as computing is easy, reliability is high, practical, for the control of entire city traffic provides information material.

The present invention is achieved by the following technical solutions, the present invention includes following steps:

1. GPS (Global Positioning System (GPS)) probe vehicles data are carried out pre-service

The GPS that can get access to (Global Positioning System (GPS)) probe vehicles data owner will comprise attributes such as vehicle location, time, state, the speed of a motor vehicle, travel direction at present.It is 0 GPS (Global Positioning System (GPS)) probe vehicles that pre-service is primarily aimed at speed on the highway section.These probe vehicles comprise two parts: speed is that 0 probe vehicles and vehicle are parked in the somewhere for a long time and travel never that to cause speed be 0 probe vehicles owing to seriously blocking up.

The former is the key component in the road section traffic volume flow analysis, is correct data; Therefore the latter is an interfering data, need differentiate accordingly and handles this part data.The method of discrimination that the present invention adopts is followed the tracks of vehicle exactly, is always if find this speed at 0 o'clock in surpassing long-time section an of signal period, shows that these data are interfering datas, when carrying out pre-service these data is rejected.

2. GPS (Global Positioning System (GPS)) probe vehicles and GIS (Geographic Information System) map are mated

Obtain road network GIS (Geographic Information System) information and pretreated GPS (Global Positioning System (GPS)) probe vehicles information that Geographic Information System provides, the position data of vehicle GPS (Global Positioning System (GPS)) is considered as diffusing point data road vertical projection towards periphery, and calculating projector distance, if wherein the shortest projector distance of certain diffusing point data is greater than the threshold value that sets in advance, then think error matching points, it is filtered out, otherwise getting the pairing road of its shortest projector distance is the travel at vehicle place, corresponding subpoint is the position after the vehicle coupling, obtain PRELIMINARY RESULTS, finish from putting the map match of line.

Three, obtain road-section average speed

The crossing is isolated into two oriented highway sections of uplink and downlink with road in the city road network.With the gps data sampled point that is in the time period T on the oriented highway section of unit is object, and it is carried out distance, time, the three-dimensional surface fitting modeling of speed, obtains this unit velocity distribution curved surface of oriented highway section on space-time in the T time period.Concrete grammar is an exponent number of determining the surface fitting model according to the number of active data point, and then the minimum M of the needed gps data point of definite surface fitting model.Then to the velocity distribution curved surface in the road direction upper integral, obtain the average velocity v in the oriented highway section of this period unit _i(t).

Four, the road network detection vehicle sampling quantity obtains

Detection vehicle sampling quantity n is accurately to calculate the needed GPS probe vehicles of each road-section average speed quantity in the road network.It depends on car speed, category of roads, road section length and detection vehicle sampling frequency f factors such as (t).Sample frequency f (t) is meant in the sampling period, and probe vehicles crosses the number of the gps data that this highway section provides, and depends on the average velocity of probe vehicles in the highway section.

Because the GP probe vehicles mainly comprises the empty wagons of not carrying and the loaded vehicle of carrying, and the cycle that empty and load sends information have very big-difference.Make L _iBe highway section i (i=1, length 2....N), T _LAnd T _HBe respectively the time of empty wagons and loaded vehicle transmission data, n _L(t) and n _H(t) be the quantity (needing obtain) of interior empty wagons of sampling period and loaded vehicle, v by statistical history GPS (Global Positioning System (GPS)) data _i(t) be the road-section average speed in sampling period.The detection vehicle sampling frequency formula of highway section i is:

$f_i\left(t\right)=\frac{n_L\left(t\right)*\frac{L_i}{v_i\left(t\right)*T_L}+n_H\left(t\right)*\frac{L_i}{v_i\left(t\right)*T_H}}{n_L\left(t\right)+n_H\left(t\right)}$

The required detection vehicle sampling quantity model of road network that the present invention proposes is:

$n\≥\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\frac{M_i}{f_i\left(t\right){\mathrm{\ϵ}}_{\mathrm{\γ}}(1-e)}$

E is GPS (Global Positioning System (GPS)) probe vehicles positioning error, ε _γBe the degree of confidence of road-section average speed, M _iMinimum value for the needed GPS of road-section average speed model of fit (Global Positioning System (GPS)) data point.

The present invention's remarkable result compared with prior art is: moving vehicle (probe vehicles) the locator data precision that applying GPS of the present invention (Global Positioning System (GPS)) information detection method gets access to is up to 95%, and data volume is big, can cover all vehicles in the road network.The space-time surface fitting model calculation speed that the present invention uses fast (be 15～25 seconds operation time) can realize obtaining synchronously in real time highway section average velocity.Therefore the present invention can obtain traffic flow state analysis required detection vehicle sampling quantity fast and accurately, for the traffic control of entire city provides in real time, information material accurately.The probe vehicles sample that application the present invention obtains carries out the city traffic analysis, and accuracy rate can reach about 90%.

Description of drawings

The FB(flow block) of the detection vehicle sampling quantity computing method that the city road network that Fig. 1 proposes for the present invention is required.

Fig. 2 is certain highway section 24 hourly average velocity variations.

Fig. 3 is the traffic flow state analysis required minimum detection vehicle sampling quantity of Shanghai City inner ring road net.3 (a) are the required minimum detection vehicle sampling quantities of trunk road network, and 3 (b) are the required minimum detection vehicle sampling quantities of secondary distributor road net, and 3 (c) are required minimum detection vehicle sampling quantities of road network, and 3 (d) are the required minimum detection vehicle sampling quantities of whole inner ring road net.

Embodiment

Below in conjunction with accompanying drawing embodiments of the invention are elaborated: present embodiment has provided detailed embodiment and process being to implement under the prerequisite with the technical solution of the present invention, but protection scope of the present invention is not limited to following embodiment.

In order to understand the method that present embodiment proposes better, choose Shanghai City inner ring road net and carry out the traffic flow modes analysis example, can be applied to the different road networks of different cities.GPS (Global Positioning System (GPS)) system vehicle satellite location data in present embodiment requires to provide and encircles one month in the Shanghai City comprises sampling car label, time, position, speed, traffic direction, information such as vehicle-state.GIS (Geographic Information System) information that also has Shanghai City inner ring road net.

As shown in Figure 1, the concrete implementation step of present embodiment is as follows:

1. GPS (Global Positioning System (GPS)) probe vehicles data are carried out pre-service:

The GPS that gets access to (Global Positioning System (GPS)) data are to store with the ID label of car.At first vehicle is followed the tracks of,, concluded that then this car is unusual vehicle, deletion this document if all velocity amplitudes of probe vehicles all are 0 according to the ID label of probe vehicles; See that then this car speed in surpassing traffic light signal section cycle length is 0 always, judge that then this time period vehicle provides invalid data, delete all information of vehicle in this time period.After abnormal data is handled GPS (Global Positioning System (GPS)) data are stored according to time sequencing, with GPS (Global Positioning System (GPS)) data storage to a file of all vehicles in 8 minutes.Conveniently carry out the dynamic traffic flow analysis.

2. GPS (Global Positioning System (GPS)) probe vehicles and GIS (Geographic Information System) map are mated:

Because the position of probe vehicles is represented with latitude and longitude coordinates in GPS (Global Positioning System (GPS)) data, therefore carry out should carrying out coordinate transform before the map match, be transformed into the urban construction coordinate among the GIS (Geographic Information System).Then 8 minutes taxi GPS (Global Positioning System (GPS)) data are read in simultaneously, and the position data point data that is considered as loosing carried out unified map match with nearest neighbor method, GPS (Global Positioning System (GPS)) locator data of vehicle is adapted on the road of vehicle '.Carry out track of vehicle according to the vehicle operating direction at last and follow the tracks of, according to the front and back contact and the road conditions of vehicle data, uncertain locator data is differentiated again, handle and obtain revised vehicle driving trace, finally finish the map match of vehicle to road.

3. obtain road-section average speed:

Each probe vehicles GPS (Global Positioning System (GPS)) data are considered as traffic sampled point (l on the highway section _i, t _i, v _i).With 8 minutes be a time period (whole day is divided into 180 periods), all GPS (Global Positioning System (GPS)) sampling number on the oriented highway section of unit is drawn surface fitting according to carrying out the space-time surface fitting, obtain velocity distribution curve.On time and direction in space, carry out integration then respectively, the average velocity v of (480 seconds) the interior highway section k that obtains 8 minutes.

$v^{\%}=\frac{{\∫}_0^{L_k}\underset{i=1}{\overset{\mathrm{\α}}{\mathrm{\Σ}}}\underset{j=0}{\overset{\mathrm{\β}}{\mathrm{\Σ}}}{a}_{\mathrm{ij}}{l}^i{t_0}^j\·\mathrm{dl}}{L_k}$

$v=\frac{\underset{0}{\overset{480}{\∫}}{v}^{\%}\mathrm{lt}}{480}$

Wherein, l is the distance of probe vehicles to the highway section starting point, and v is highway section t ₀Instantaneous average velocity constantly.a _IjBe the coefficient of polynomial fitting, determine by the GPS in the sampling period (Global Positioning System (GPS)) data message.α, the high reps of l and t when β is match is by the effectively number of GPS (Global Positioning System (GPS)) data point decision on the match highway section.Concrete value is as shown in table 1:

GPS (Global Positioning System (GPS)) data message	[9，12]	[6，8]	[3，5]
				(α，β)	(2，3)	(2，2)	(1，1)
M	9	6	3

Table 1

GPS (Global Positioning System (GPS)) data is the number of effective GPS (Global Positioning System (GPS)) data point on the highway section, has determined α in the model of fit, the number of times of β.M is the minimum value of the needed GPS of model of fit (Global Positioning System (GPS)) data point.Consider from the finiteness of data and actual road conditions, choose MAX (α)=2, MAX (β)=3 in this example.Fig. 2 is certain average velocity of 24 hours in highway section that the method choice of dynamical model of fit according to table one calculates.

4. obtaining of road network detection vehicle sampling quantity:

The historical data of statistics GPS (Global Positioning System (GPS)) probe vehicles calculates in average one day the quantity of loaded vehicle and empty wagons in each period road network.The cycle of choosing the loaded vehicle feedback information is 2 minutes, and the cycle of empty wagons feedback information is 20 seconds.Calculate the sample frequency f (t) of each period according to the sample frequency formula.Because the probe vehicles data volume in road network section in time alters a great deal, so counts self-adaptation according to actual detection car in the road network in this example and choose model of fit calculating sampling amount.Table two has been listed traffic flow state analysis required minimum GPS (Global Positioning System (GPS)) detection vehicle sampling quantity of ring in method that self-adaptation chooses model order and the different period Shanghai City.Self-adaptation is chosen the traffic flow analysis model method and result of calculation sees table 2 for details:

Period	0:00—5:00	5:00—8:00	8:00—20:00	20:00—24:00
					Approximating method	A surface fitting	The quadric surface match	The cubic surface match	The quadric surface match
(α，β)	(1，1)	(2，3)	(3，3)	(1，1)
					Minimum detection vehicle sampling quantity ()	1500	2500	3000	2000

Table 2

Fig. 3 adopts the self-adaptation surface fitting model of table 2 and the traffic flow state analysis required minimum detection vehicle sampling quantity of Shanghai City inner ring road net that the cubic surface model of fit calculates respectively.Wherein a is the required minimum detection vehicle sampling quantity of trunk road network, and b is the required minimum detection vehicle sampling quantity of secondary distributor road net, and c is a required minimum detection vehicle sampling quantity of road network, and d is the required minimum detection vehicle sampling quantity of whole inner ring road net.Wherein be about 3000 daytime, and this and the last true road conditions of encircling have through the country kept good consistance.

From present embodiment as can be seen: GPS (Global Positioning System (GPS)) the probe vehicles sample that obtains according to present embodiment can be used for the traffic flow modes analysis of city road network effectively.

Claims (3)

1, a kind of acquisition methods of traffic flow state analysis required detection vehicle sampling quantity is characterized in that, may further comprise the steps:

1. GPS probe vehicles data are carried out pre-service, vehicle is followed the tracks of,, conclude that then this car is unusual vehicle, deletion this document if all velocity amplitudes of GPS probe vehicles all are 0; If the speed of finding the GPS probe vehicles is always at 0 o'clock in surpassing long-time section an of signal period, show that these data are interfering datas, when carrying out pre-service, these data are rejected;

2. GPS probe vehicles and GIS map are mated;

3. obtain road-section average speed;

4. the road network detection vehicle sampling quantity obtains;

Described detection vehicle sampling quantity, its value n, be accurately to calculate the needed GPS probe vehicles of each road-section average speed quantity in the road network, it depends on car speed, category of roads, road section length and detection vehicle sampling frequency f (t), sample frequency f (t) was meant in the sampling period, probe vehicles crosses the number of the gps data that this highway section provides, and depends on the average velocity of probe vehicles in the highway section;

Described GPS probe vehicles comprises the empty wagons of not carrying and the loaded vehicle of carrying, makes L _iBe the length of highway section i, i=1,2....N, T _LAnd T _HBe respectively the time of empty wagons and loaded vehicle transmission data, n _L(t) and n _H(t) be the quantity of interior empty wagons of sampling period and loaded vehicle, need obtain v by the statistical history gps data _i(t) be the road-section average speed in sampling period, the detection vehicle sampling frequency formula of highway section i is:

$f_i\left(t\right)=\frac{n_L\left(t\right)*\frac{L_i}{v_i\left(t\right)*T_L}+n_H\left(t\right)*\frac{L_i}{v_i\left(t\right)*T_H}}{n_L\left(t\right)+n_H\left(t\right)};$

The required detection vehicle sampling quantity model of road network is:

$n\≥\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\frac{M_i}{f_i\left(t\right){\mathrm{\ϵ}}_{\mathrm{\γ}}(1-e)}$

E is a GPS probe vehicles positioning error, ε _γBe the degree of confidence of road-section average speed, M _iMinimum value for the needed gps data point of road-section average speed model of fit.

2, the acquisition methods of traffic flow state analysis required detection vehicle sampling quantity according to claim 1, it is characterized in that, described GPS probe vehicles and GIS map are mated, be meant: obtain road network GIS information and pretreated GPS probe vehicles information that Geographic Information System provides, the position data of vehicle GPS is considered as diffusing point data road vertical projection towards periphery, and calculating projector distance, if wherein the shortest projector distance of certain diffusing point data is greater than the threshold value that sets in advance, then think error matching points, it is filtered out, otherwise getting the pairing road of its shortest projector distance is the travel at vehicle place, corresponding subpoint is the position after the vehicle coupling, obtain PRELIMINARY RESULTS, finish from putting the map match of line.

3, the acquisition methods of traffic flow state analysis required detection vehicle sampling quantity according to claim 1, it is characterized in that, the described road-section average speed of obtaining, be meant: the crossing is isolated into two oriented highway sections of uplink and downlink with road in the city road network, with the gps data sampled point that is in the time period T on the oriented highway section of unit is object, it is carried out distance, time, the three-dimensional surface fitting modeling of speed, obtain this unit velocity distribution curved surface of oriented highway section on space-time in the T time period; Determine the exponent number of surface fitting model then according to the number of active data point, and then the minimum M of the needed gps data point of definite surface fitting model, then to the velocity distribution curved surface in the road direction upper integral, obtain the average velocity v in the oriented highway section of this period unit _i(t).

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