WO2017206025A1

WO2017206025A1 - A system and method for estimating parking availability

Info

Publication number: WO2017206025A1
Application number: PCT/CN2016/083936
Authority: WO
Inventors: Weiran NIE
Original assignee: Harman International Industries, Incorporated
Priority date: 2016-05-30
Filing date: 2016-05-30
Publication date: 2017-12-07

Abstract

A method for estimating the traffic flow volume into a parking facility (170) is provided. The method comprises estimating the traffic flow volume into all exits of a parking facility (170); and summing all traffic flow volumes, wherein the step of estimating the traffic flow volume into an exit (160) comprises: estimating a main road traffic flow volume at a first location (140) and a main road traffic flow volume at a second location (150); and subtracting the main road traffic flow volume at the second location (150) from the main road traffic flow volume at the first location (140) to obtain a first side change volume. With this method, parking availability can be known without costly investment.

Description

A SYSTEM AND METHOD FOR ESTIMATING PARKING AVAILABILITY

FIELD

This invention relates to the field of vehicle parking and more particularly to methods and systems for determining parking space availability.

BACKGROUND

Parking has been an increasingly serious problem in many cities. Drivers want to know the availability of parking facilities near their destinations. Some parking garages have started to provide some advanced system, like using video-based solution to determine the availability of parking spaces and it can provide accurate information regarding parking availability. However, the cost for such system is considerable high.

SUMMARY

According to one embodiment, a method for estimating the traffic flow volume into a parking facility is provided. The method comprises estimating the traffic flow volume into all exits of a parking facility； and summing all traffic flow volumes, wherein the step of estimating the traffic flow volume into an exit comprises: estimating a main road traffic flow volume at a first location and a main road traffic flow volume at a second location； and subtracting the main road traffic flow volume at the second location from the main road traffic flow volume at the first location to obtain a first side change volume, wherein the first location and the second location are on the two sides of the exit along the main road, and there is no branch road between the first location and the second location.

In some embodiments, the step of estimating the traffic flow volume into an exit further comprises: estimating a main road traffic flow volume at a third location and a main road traffic flow volume at a fourth location； subtracting the main road traffic flow volume at the fourth location from the main road traffic flow volume at the third location to obtain the second side change volume, and summing the first side change volume and the second side change volume, wherein, the third location and the fourth location are on the opposite position of the second location and the first position across the main road, and there is no branch road between the third location and the fourth location.

In some embodiments, the step of estimating the main road traffic flow volume comprises: dividing a traffic flow velocity by a vehicle spacing to obtain a real-time single lane flow parameter； multiplying the real-time single lane flow parameter by a lane number to obtain a real-time flow parameter； and integrating the real-time flow parameter over time to obtain the main road traffic flow volume.

In some embodiments, the vehicle spacing is estimated based on the vehicle velocity, lighting condition, slipperiness of the main road, and the ration of four-wheel vehicles of all traffic units.

In some embodiments, the traffic flow velocity is the average velocity of probe vehicles.

In some embodiments, the distance between the first location and the exit is estimated by the posted speed multiplying a time of two seconds divided by a unit-conversion coefficient.

In some embodiments, the average velocity of probe vehicles is obtained by the probe vehicles sending their GPS data.

According to one embodiment, a device for estimating the traffic flow volume into a parking facility is provided. The device comprises a plurality of sub-flow estimators estimating the traffic flow volume into all exits of a parking facility； and a totally traffic flow volume unit summing all traffic flow volumes, wherein the sub-flow estimator comprises: a first location estimator estimating a main road traffic flow volume at a first location and a second location estimator estimating a main road traffic flow volume at a second location； and a first side change volume estimator subtracting the main road traffic flow volume at the second location from the main road traffic flow volume at the first location to obtain a first side change volume, wherein the first location and the second location are on the two sides of the exit along a main road, and there is no branch road between them.

In some embodiments, the sub-flow estimator further comprises a third location estimator estimating a main road traffic flow volume at a third location and a fourth location estimator estimating a main road traffic flow volume at a fourth location； and a second side change volume estimator subtracting the main road traffic flow volume at the fourth location from the main road traffic flow volume at the third location to obtain the second side change volume, wherein the sub-flow estimator summing the first side change volume and the second side change volume, the third location and the fourth location being on the opposite position of the second location and the first position across the main road, and there being no branch road between the third location and the fourth location.

In some embodiments, the first location estimator and the second location estimator comprise: a real-time single lane flow parameter unit dividing a traffic flow velocity by a vehicle spacing to obtain the real-time single lane flow parameter； a real-time flow parameter unit multiplying the real-time single lane flow parameter by lane number to obtain a real-time flow parameter； and an integrator integrating the real-time flow parameter over time to obtain the traffic flow volume.

In some embodiments, the traffic flow velocity is the average velocity of the probe vehicles.

In some embodiments, the distance between the first location and the exit is estimated by the posted speed multiplying a time of 2 seconds divided by a unit-conversion coefficient.

In some embodiments, the average velocity of the probe vehicles is obtained by the probe vehicles sending their GPS data.

According to one embodiment, one or more computer-readable storage devices encoding computer-executable instructions that when executed by a computing processor on a computer system, cause the computing processor to perform a computer process are provided, the computer process comprising: estimating the traffic flow volume into all exits of a parking facility； and summing all traffic flow volumes, wherein the process of estimating the traffic flow volume into an exit comprises: estimating a main road traffic flow volume at a first location and a main road traffic flow volume at a second location； and subtracting the main road traffic flow volume at the second location from the main road traffic flow volume at the first location to obtain the first side change volume, wherein the first location and the second location are on the two sides of the exit along the main road, and there is no branch road between them.

In some embodiments, the process of estimating the traffic flow volume into an exit further comprises: estimating a main road traffic flow volume at a third location and a main road traffic flow volume at a fourth location； subtracting the main road traffic flow volume at the fourth location from the main road traffic flow volume at the third location to obtain the second side change volume, and summing the first side change volume and the second side change volume, wherein, the third location and the fourth location are on the opposite position of the second location and the first position across the main road, and there is no branch road between the third location and the fourth location.

In some embodiments, the process of estimating the main road traffic flow volume comprises: dividing a traffic flow velocity by a vehicle spacing to obtain a real-time single lane flow parameter； multiplying the real-time single lane flow parameter by a lane number to obtain a real-time flow parameter； and integrating the real-time flow parameter over time to obtain the main road traffic flow volume.

According to one embodiment, a system for estimating parking availability of a target parking facility is provided, the system comprises transmitters on a plurality of probe vehicles nearby the parking facility, each transmitter sending the respective probe vehicle’s real time velocity and location； and a server estimating parking availability based on the velocities and locations sent by the transmitters and information about the capacity of the target parking facility at the beginning of a measurement cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and are, therefore, not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings.

Figure 1 illustrates a uni-direction main road near a parking facility exit；

Figure 2 illustrates vehicle’s velocity change according to the distance from exit；

Figure 3 illustrates a bi-direction main road near a parking facility exit；

Figure 4 illustrates an example system for estimating the traffic flow volume into a parking facility, according to one embodiment of the present invention；

Figure 5 illustrates a flow chart of a method for estimating the traffic flow volume into a parking facility, according to one embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

Nowadays, more and more vehicles are equipped with a GPS unit and it has become common for Taxi cabs and public transportation vehicles such as buses being required to install GPS unit on board, which log vehicle position, speed and heading information at regular time intervals. Using taxis as city traffic probes, the disclosed solution includes a system and method to estimate the traffic flow volume at selected road segments near the exit of the target parking facility. Based on that, the number of vehicles entering/leaving the target parking facility can be estimated in real-time. Parking availability is derived based on the ratio of the net traffic flow entering the parking facility and its capacity at the beginning of the measurement cycle. Here, a parking facility refers to a parking lot or a parking garages.

Figure 1 illustrates a parking facility and its nearby road to describe the disclosed system. The road enclosing the target parking facility is referred to as a main road 100. The junction of the main road 100 and a side road 110 leading to the target parking facility is referred to as an exit 160 of the parking facility. Here, the main road 100 is uni-direction and the side road 110 is exit-only. The location of exit 160 can be determined precisely via the map database unit.

A first location 140 and a second location 150 are selected on the both sides of the exit 160 along the main road 100. No branch road exits between the first location 140 and the second location 150. The distance between the first location 140 and the exit 160, denoted by d in Figure 1, should be large enough so that the vehicle’s speed on the main road will not be affected by the vehicle exiting the side road 110, if any.

One way to determine the distance d is based on the reaction time needed for a drive to hit the brake pedal when he or she sees some car exiting the side road 110. Assume the reaction time is 2 seconds and suppose the posted speed of the main road is 40 km/h, then d should be at least set to 40/3.6×2 ＝ 22 m, where 3.6 is the unit-conversion coefficient. The idea is that the estimation of flow average speed at the first location 140 shall not be affected by the vehicle exiting the side road 110.

The second location 150 can be selected in several ways. For example, the parameter d’ , which denotes the distance between the second location 150 and the exit 160 can be the same as d, the distance between the first location 140 and the exit 160. Or, suppose there are vehicles exiting side road 110, then the vehicles on the main road 100 is likely to be slowed down. By analyzing the spatial distribution of the estimated flow average speed, the second location 150 and corresponding d’ can be identified where the lowest flow average speed is logged, as illustrated in Figure 2. In Figure 2, the x axis represents the horizontal distance measured from the location of the exit 160, with negative distance representing locations behind the exit 160. Both d and d’ are shown in Figure 2.

In the scenario as illustrated by Figure 1, the volume of vehicles entering the target parking facility is calculated as:

vol_ {target} (t0, t1) ＝ vol_ {140} (t0, t1) –vol_ {150} (t0, t1) (1)

wherein vol_ {target} (t0, t1) denotes the volume of vehicles entering the target facility during a time span of [t0, t1] , vol _ {140} (t0, t1) and vol _ {150} (t0, t1) denote the volumes of vehicles passing by the first location 140 and the second location 150 during the time span of [t0, t1] .

Figure 3 illustrates a bi-directional main road with a forward lane 300 and a reverse lane 320 and bi-direction side road 310 of the target parking facility 370. Vehicles exiting target parking facility 370 can turn right and enter the forward lane 300, or turn left and enter the reverse lane 320. A first location 340 and a second location 350 are selected to estimate the traffic flow change on lane 300, using the principles presented in the aforementioned description. Similarly, a third location 360 and a fourth location 370 are selected to estimate the traffic flow change on lane 320, and they can be selected on the opposite position of the second location 350 and the first position 340 across the main road.

The traffic flow change volume on the forward lane 300 is calculated as:

vol_ {300} (t0, t1) ＝ vol_ {340} (t0, t1) –vol_ {350} (t0, t1) (2)

The traffic flow change volume on the reverse lane 320 is calculated as:

vol_ {320} (t0, t1) ＝ vol_ {360} (t0, t1) –vol_ {370} (t0, t1) (3)

The traffic flow volume entering/exiting the target facility is the sum of the traffic flow changes volume on the forward lane 300 and the reverse lane 320, and it can be expressed as:

vol_ {target} (t0, t1) ＝ vol_ {300} (t0, t1) + vol_ {320} (t0, t1) ＝

vol_ {340} (t0, t1) –vol_ {350} (t0, t1) + vol_ {360} (t0, t1) –vol_ {370} (t0,

t1) (4)

The traffic flow volume passing a location, like the first location 140 and the second location 150 in Figure 1 or the first to

fourth locations

340, 350, 360 and 370 are estimated according to the following step. In the disclosed system, the speed of a traffic flow v (t) is defined as the average of the individual speeds of all the vehicles passing a certain point. It can be estimated based on the mean speed of all probe vehicles passing the area. A multiplicative factor between 0 and 1 may be applied to scale down the mean speed of probe vehicles, taking into account that taxi drivers are usually more experienced and aggressive than average drivers.

Vehicle spacing s (t) is the estimated distance between the front bumper of the leading vehicle and the front bumper of the following vehicle when the vehicles are on a busy road. The safe spacing to reduce the risk of collision in a traffic flow strongly depends on the traffic mean speed, e.g., when the traffic flow is stagnant, vehicles tend to follow very closely； on the other hand, when the traffic drives at or above the posted speed limit, the spacing between vehicles would be substantially larger. Other factors also affecting the safe spacing include weather, lighting, and traffic mix. A method is to establish a linear regression model between s, v and other potential factors:

s(t) ＝ w0 + w1×v (t) + w2×l + w3×w + w4×m (5)

where w0 through w4 are parameters of the linear regression model； l denotes the lighting condition in unit of lux； w denotes the weather index between 0 and 1 indicating the slipperiness of the roadway； m denotes the traffic mix indicating the ratio of four-wheel vehicles of all the traffic units including two-wheel vehicles and pedestrians. The linear model can be fitted with data collected using conventional tools of transportation engineering, e.g., loop detectors and traffic cameras at specific road segments. Once the model is built, it can be generalized to similar road segments with no loop detectors and traffic cameras. More sophisticated models than linear regression may also be used.

As an example, one fitted linear regression model for a busy urban road segment with moderate road lighting is:

s(t) ＝ 0.08+0.80v (t) -0.09l+0.45w-0.16m (6)

where v, l, w and m are normalized variables whose values range from 0 to 1. The coefficients (0.80, -0.09, etc. ) for each variable correspond to relative importance/weights. While v and w are positively related to the safety spacing, i.e., the higher the speed or the more slippery the road surface, the larger the safety spacing should be； l and m are negatively correlated with s (t) , i.e., the dimmer the lighting condition or the more pedestrian/two-wheelers on the road, the larger the safety spacing should be.

The flow parameter f (t) denotes the rate at which vehicles (both probe and non-probe) pass a given location at time t, the relation between flow f (t) , speed v (t) and spacing s (t) on a given location is expressed as:

f(t) ＝ v (t) /s (t) (7)

The number of vehicles passing a given location during a certain time interval [t0, t1] , denoted as vol (t0, t1) can be expressed as the integral of f (t) over the time span of [t0, t1] . This is under the assumption that the road is a single-lane road. If not, then f (t) should be multiplied by the lane number.

Note that the disclosed method is just one possible way of deriving flow parameter f (t) , other implementations can be used to derive flow/volume directly or indirectly based on probe vehicle data. In Figure 1, the volume of vehicles passing by the first location 140 (vol _ {140} (t0, t1) ) can be estimated by integrating f (t) at the first location 140 over the time span of [t0, t1] . Likewise, in Figure 3, the volume of vehicles passing by the third location 350 (vol _ {350} (t0, t1)) can be estimated by integrating f (t) at the first location 350 over the time span of [t0, t1] .

Figure 4 illustrates an example system for estimating the traffic flow volume into a parking facility. There are a number of vehicles moving on roads nearby a parking facility. Several vehicles are equipped with GPS and they are the probe vehicles 402. These probe vehicles are in connection remotely with a server 401, sending vehicle information including velocity and location to the server. The server selects reference locations and, based on the received information, estimates the traffic flow volume into a parking facility according to the methods described above. The server may have real time information about weather, lighting, and traffic mix in the target area, or have predetermined information for them. The server has knowledge about the capacity of the target parking facility at the beginning of a measurement cycle, which can be obtained by a reporter or using statistical data collected prior to beginning the measurement cycle. Then, based on the real time traffic flow volume into a parking facility, the parking availability information can be obtained. A color scheme can be used to indicate the resource scarcity of the target parking facility. If the net traffic flow entering the target facility exceeds a pre-determined threshold, e.g., 2/3 of the facility’s capacity, a corresponding color, e.g., red, will be displayed on the icon representing the target facility. The server may be able to send the parking availability information to apps installed in mobile phones, radio stations, TV stations, or disclose such information on some websites.

The example hardware and operating environment of Figure 4 for implementing the described technology includes a computing device, such as general purpose computing device. For example, the computer includes a processing unit, a system memory, and a system bus that operatively couples various system components including the system memory to the processing unit. There may be only one or there may be more than one processing unit, such that the processor of computer comprises a single central-processing unit (CPU) , or a plurality of processing units, commonly referred to as a parallel processing environment. The computer may be a conventional computer, a distributed computer, or any other type of computer； the invention is not so limited. The embodiments of the invention described herein are implemented as logical steps in one or more computer systems including the computing device.

Figure 5 illustrates the steps of the disclosed method according to one embodiment. At step 501, the server selects a first location before the exit of the target parking facility. The distance between the first location and the exit of the target parking facility should be large enough so that the speed on the main road will not be affected by the vehicle entering or exiting the side road. At step 502, the server selects a second location after the exit of the target parking facility.

At step 503, the server estimates the traffic flow volume passing the exit by subtracting the traffic flow volume at the second location from the traffic flow volume at the first location.

At step 504, the server checks whether there is another exit for the parking facility. And if there is, then the server repeats step 501.

At step 505, the server estimates the net traffic flow entering the target parking facility by summing the traffic flow volume passing all the exits of the target parking facilities.

At step 506, the server estimates the real-time parking availability information based on the known capacity of the parking facility and the net traffic flow.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims

A method for estimating the traffic flow volume into a parking facility, comprising:

estimating the traffic flow volume into all exits of a parking facility； and

summing all traffic flow volumes, wherein

the step of estimating the traffic flow volume into an exit comprises:

estimating a main road traffic flow volume at a first location and a main road traffic flow volume at a second location； and

subtracting the main road traffic flow volume at the second location from the main road traffic flow volume at the first location to obtain a first side change volume, wherein

the first location and the second location are on the two sides of the exit along the main road, and there is no branch road between the first location and the second location.
The method according to claim 1, wherein the step of estimating the traffic flow volume into an exit further comprises:

estimating a main road traffic flow volume at a third location and a main road traffic flow volume at a fourth location；

subtracting the main road traffic flow volume at the fourth location from the main road traffic flow volume at the third location to obtain the second side change volume, and

summing the first side change volume and the second side change volume, wherein, the third location and the fourth location are on the opposite position of the second location and the first position across the main road, and there is no branch road between the third location and the fourth location.
The method according to claim 1 or claim 2, wherein the step of estimating the main road traffic flow volume comprises:

dividing a traffic flow velocity by a vehicle spacing to obtain a real-time single lane flow parameter；

multiplying the real-time single lane flow parameter by a lane number to obtain a real-time flow parameter； and

integrating the real-time flow parameter over time to obtain the main road traffic flow volume.
The method according to claim 3, wherein the vehicle spacing is estimated based on the vehicle velocity, lighting condition, slipperiness of the main road, and the ration of four-wheel vehicles of all traffic units.
The method according to claim 3, wherein the traffic flow velocity is the average velocity of probe vehicles.
The method according to claim 1, wherein the distance between the first location and the exit is estimated by the posted speed multiplying a time of two seconds divided by a unit-conversion coefficient.
The method according to claim 5, wherein the average velocity of probe vehicles is obtained by the probe vehicles sending their GPS data.
A device for estimating the traffic flow volume into a parking facility, comprising:

a plurality of sub-flow estimators estimating the traffic flow volume into all exits of a parking facility； and

a totally traffic flow volume unit summing all traffic flow volumes, wherein

the sub-flow estimator comprises:

a first location estimator estimating a main road traffic flow volume at a first location and a second location estimator estimating a main road traffic flow volume at a second location； and

a first side change volume estimator subtracting the main road traffic flow volume at the second location from the main road traffic flow volume at the first location to obtain a first side change volume, wherein

the first location and the second location are on the two sides of the exit along a main road, and there is no branch road between them.
The device according to claim 8, wherein the sub-flow estimator further comprises

a third location estimator estimating a main road traffic flow volume at a third location and a fourth location estimator estimating a main road traffic flow volume at a fourth location； and

a second side change volume estimator subtracting the main road traffic flow volume at the fourth location from the main road traffic flow volume at the third location to obtain the second side change volume, wherein

the sub-flow estimator summing the first side change volume and the second side change volume, the third location and the fourth location being on the opposite position of the second location and the first position across the main road, and there being no branch road between the third location and the fourth location.
The device according to claim 8 or claim 9, wherein the first location estimator and the second location estimator comprise:

a real-time single lane flow parameter unit dividing a traffic flow velocity by a vehicle spacing to obtain the real-time single lane flow parameter；

a real-time flow parameter unit multiplying the real-time single lane flow parameter by lane number to obtain a real-time flow parameter； and

an integrator integrating the real-time flow parameter over time to obtain the traffic flow volume.
The device according to claim 10, wherein the vehicle spacing is estimated based on the vehicle velocity, lighting condition, slipperiness of the main road, and the ration of four-wheel vehicles of all traffic units.
The device according to claim 10, wherein the traffic flow velocity is the average velocity of the probe vehicles.
The device according to claim 8, wherein the distance between the first location and the exit is estimated by the posted speed multiplying a time of 2 seconds divided by a unit-conversion coefficient.
The device according to claim 12, wherein the average velocity of the probe vehicles is obtained by the probe vehicles sending their GPS data.
One or more computer-readable storage devices encoding computer-executable instructions that when executed by a computing processor on a computer system, cause the computing processor to perform a computer process, the computer process comprising:

estimating the traffic flow volume into all exits of a parking facility； and

summing all traffic flow volumes, wherein

the process of estimating the traffic flow volume into an exit comprises:

estimating a main road traffic flow volume at a first location and a main road traffic flow volume at a second location； and

subtracting the main road traffic flow volume at the second location from the main road traffic flow volume at the first location to obtain the first side change volume, wherein

the first location and the second location are on the two sides of the exit along the main road, and there is no branch road between them.
The One or more computer-readable storage devices according to claim 15, wherein the process of estimating the traffic flow volume into an exit further comprises:

estimating a main road traffic flow volume at a third location and a main road traffic flow volume at a fourth location；

subtracting the main road traffic flow volume at the fourth location from the main road traffic flow volume at the third location to obtain the second side change volume, and

summing the first side change volume and the second side change volume, wherein, the third location and the fourth location are on the opposite position of the second location and the first position across the main road, and there is no branch road between the third location and the fourth location.
The One or more computer-readable storage devices according to claim 15 or claim 16, wherein the process of estimating the main road traffic flow volume comprises:

dividing a traffic flow velocity by a vehicle spacing to obtain a real-time single lane flow parameter；

multiplying the real-time single lane flow parameter by a lane number to obtain a real-time flow parameter； and

integrating the real-time flow parameter over time to obtain the main road traffic flow volume.
A system for estimating parking availability of a target parking facility, comprising:

transmitters on a plurality of probe vehicles nearby the parking facility, each transmitter sending the respective probe vehicle’s real time velocity and location； and

a server estimating parking availability based on the velocities and locations sent by the transmitters and information about the capacity of the target parking facility at the beginning of a measurement cycle.