Flow velocity prompting system and method based on traffic flow parameters

Abstract

The invention relates to a flow velocity prompting system and method based on traffic flow parameters. The road traffic capacity is the maximum traffic volume (flow) which can be borne by a certain road facility. Flow definition is as follows: flow q = N / t is irrelevant to V, q = KV is relevant to KV product, large flow can be achieved at slow speed, and in order to reflect the flow at the speed, a new traffic flow parameter flow velocity is provided, and the expression is D = Vq. And deducing a traffic jam and dissipation judgment inequality # imgabs0 # by using D, and establishing an iterative nonlinear equation of the flow velocity D, the density K and the headstock, wherein the flow velocity can quantitatively identify the smooth traffic congestion jam state. A traffic flow parameter flow velocity prompting system is provided, the traffic flow parameter flow velocity prompting system is installed on an automobile, human driving behaviors are optimized and standardized, people drive at the flow velocity D larger than D1, the road traffic capacity can be improved, blockage can be reduced, and the flow velocity D is smaller than D2, and X is larger than X. Safety can be improved during driving, traffic accidents are reduced, and great social benefits are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of traffic flow parameter and flow speed prompting, and in particular to a traffic flow parameter and flow speed prompting system and method. Background Art

[0002] Traffic flow refers to the traffic state formed by a group of vehicles traveling on the road. Generally, the maximum flow rate of traffic flow is used to measure the road capacity. The maximum flow rate q = KV has different combinations of KV. Slow speed can also achieve a large flow rate, but slow speed is obviously not the road capacity that humans pursue. This is because the definition of flow rate q = N / t (the number of vehicles passing within time t, Veh / h) has nothing to do with speed.

[0003] The number of cars is growing very fast, with annual sales of more than 30 million, but road construction cannot keep up with the speed of car development, which will cause road traffic congestion and become increasingly serious. Therefore, the present invention provides a flow velocity prompt system and method based on traffic flow parameters, which uses flow velocity to optimize the design of road capacity, optimizes and regulates human driving behavior to improve road capacity, improves driving safety, reduces traffic accidents, and solves the problem of increasingly serious road traffic congestion. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a flow velocity prompt system and method based on traffic flow parameters to solve the problem of increasingly serious road traffic congestion.

[0005] In order to solve the above technical problems, the technical solution of the present invention is: a method for prompting flow speed based on traffic flow parameters, comprising:

[0006] Step S1, according to the definition of flow rate and speed, a new traffic flow parameter velocity is proposed, and its expression is D = Vq; Step S2, taking section A of the road as the observation point, observing the actual data of the velocity D, and calculating μmean value, using mathematical statistics to calculate variance σ 2 . n is a natural number. According to u, σ 2 Optimize the design of road capacity and optimize the determination of D1 and D2 values, where D1 is the minimum flow rate and D2 is the maximum flow rate. You can also try to determine the D1 and D2 values ​​based on the design status at the beginning of road construction. Mark D1 and D2 on road signs.

[0007] Step S3, using the flow rate D parameter, optimize and regulate human driving behavior D1<D<D2, X>X. D1 is the minimum flow rate on the road, D2 is the maximum flow rate on the road. Dmax is the road capacity index. X0 is the saturated headway.

[0008] Step S4, based on steps S1 to S3, a traffic flow parameter flow speed prompt system is established.

[0009] Preferably, in step S1, a new traffic flow parameter velocity is proposed, represented by the letter D:

[0010] D=Vq (1)

[0011] Among them, D traffic flow speed (Vehkm / h 2 )q is the traffic flow or flow (Veh / h); V is the speed, including the location speed (km / h); D represents the flow velocity of vehicles passing through the observation section or location at time t with a speed of V, which can be expressed by i:

[0012] D i =V i q i or

[0013] Among them, V i is the location speed, D i is the location flow velocity.

[0014] Preferably, the measurement method is as follows: at section A, start timing t0=0 at section A, and after a period of time t i , record the number of vehicles passing through N i , and use a tachometer to record the location speed V i , a counting sensor is set on the monitoring recorder on the road, that is, recording V i Record N at the same time i and t i , use V i Location speed, t i 、V i Easy to measure, avoid K i Not easy to measure.

[0015] Preferably, in step S2, starting from the physical meaning of flow velocity, the traffic state can be divided into two parts: free flow state and non-free flow state: the traffic flow characteristics of the non-free flow state: the front vehicle or overtaking or ramp entering the main road or reverse process affects the speed of the rear vehicle or changes the traffic flow state of the rear vehicle; if saturation is reached, such as 2400veh / h / 1n or a certain value is a saturated state. At this time, the flow rate is a saturated flow rate q0. In this state, the maximum density corresponding to any speed satisfies VK0=q0, and the K0 value is a saturated density; the corresponding head spacing is a saturated spacing X0, that is, the minimum safe distance at this speed. The corresponding speed is the saturated speed, represented by V0, and can also be expressed by critical density or critical speed. D i There is no additive property, but the average value can be calculated as follows: use The average flow rate can reflect the actual state of traffic flow rate, where D is a countable, finite, discontinuous parameter and n is a natural number.

[0016] Preferably, the flow rate calculation formula (2) can be obtained: make is the average headway time, Ruodang For N i Car and N n－1 The headway time of the vehicle is t i ,but:

[0017]

[0018] Where D i Unit: Veh.km / h 2 , t i Unit: S / veh;

[0019] Same reason is the average headway, if N i With N i－1 Headroom X i , (unit: m / Veh) then:

[0020]

[0021] Formula (4) D i With V i 2 Proportional to X i Inversely proportional, when driving on the road, there is a speed limit, the speed has an upper limit, and the headway has a minimum value, then There is a maximum value;.

[0022] Congestion speed V<20km / h, Dcongestion=20×1600=32kVehKm / h 2 , D max =(80~120)×(1800~2400)=(144~288)kVehkm / h 2 , use D max Using flow velocity as a measure of road capacity avoids the contradiction that large flow volume and possibly slow speed are used as the basis for road capacity.

[0023] Preferably, take section A as the observation point and calculate the flow rate Stable value, according to this phenomenon, if q i =V i K i =q i +1=V i +1K i﹢1, then it is understood that car i leaves and i﹢1 enters, and i and i﹢1 are the front and back relationship of the vehicle space;

[0024] Velocity iteration equation: velocity and headway on a one-dimensional road section under non-free flow conditions, The formula for speed and headway distance is It is deduced that:

[0025]

[0026] like and There is an angle a, then:

[0027]

[0028] Formula (6) is cosa squared, indicating that the angle between the ramp and the main road is sensitive to the flow velocity and has a greater impact, indicating that the angle of the leading vehicle overtaking is sensitive to the flow velocity of the following vehicle.

[0029] A flow velocity prompting system based on traffic flow parameters, comprising:

[0030] A vehicle speed signal collection unit is used to obtain vehicle speed data;

[0031] Collect the front and rear vehicle head-to-tail distance signal unit, used to measure the distance from the cab to the rear of the front vehicle;

[0032] Processing, analysis and calculation unit, used to receive speed and distance to calculate D, X0;

[0033] Output command unit, used to issue instructions to the driver according to the calculation results of D and X0;

[0034] The driving status prompt unit is used to remind the driver to perform corresponding flow speed operations.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The method of the present invention is used to extract speed information from the car, and then the distance S to the front car is measured by radar or laser, in meters, X i=S+S1, S is the distance from the cab of the vehicle to the rear of the vehicle in front, S1 is the distance from the rear of the vehicle in front to the front window of the cab of the vehicle in front, the traffic flow parameter velocity prompt system is installed on the front window of the cab, and is automatically calculated using formula (4). When it is lower than a certain value, the traffic flow parameter velocity prompt system reminds the driver to increase the velocity (i.e., accelerate). First look at the speed meter. Low velocity generally means low speed. Acceleration is used to increase the speed. While increasing the speed, the distance between the front of the vehicle naturally decreases. At the same time, acceleration will increase the flow rate. The combined effect of the velocity is rapidly increased. If the velocity is high, braking is used to reduce the speed. While reducing the speed, the distance between the front of the vehicle naturally increases, and the velocity decreases rapidly. This is used to control the vehicle velocity and increase traffic efficiency.

[0037] 2. In actual application, when When D1 is at the minimum value and D2 is at the maximum value, the green light is on. i >D2(such as 264kVehkm / h 2 ) or vehicle distance X i <X0 The red light is on, reminding that the flow rate is too high or the headroom is too small, and the instrument emits a warning sound. i Lower than D1 (such as 160kVehkm / h 2 ), the traffic flow parameter velocity prompt system will sound a prompt, telling you that the velocity is too low and needs to be increased.

[0038] 3. The traffic flow parameter flow prompt system on highways and expressways has different settings for D1 and D2, and uses instrument traffic lights and audio functions to remind, which can increase the flow rate. During holidays, it can ensure that vehicles travel at a higher flow rate, improve road capacity, and reduce congestion. It also avoids overtaking due to excessive vehicle intervals, which reduces speed.

[0039] 4. The current road has a maximum speed limit of Vmax, but no minimum safe headway distance Xmin is required, which can easily cause traffic accidents. It is difficult and unscientific to stipulate X alone, because X is related to V. The larger the V, the larger the X, and the smaller the V, the smaller the X. X is a function of V. Using the flow rate D (1000V 2 / X) model can overcome this problem. When D is constant, dX 2 / dV 2 =2000 / D>0, indicating that the rate of change of X to V dX / dV increases with the increase of V, and the safety distance X increases rapidly with the increase of speed V. D=1000V 2 / X model guides driving more safely. For double insurance, the prompt system sets the saturated headway X0, press X i>X0 prompts driving. X0 is calculated according to the basic free flow speed and basic traffic capacity of the basic section of the industry standard JTD-2017 "Highway Route Design Specifications" of the People's Republic of China, that is, the saturated flow q0, X0 = 1000V0 / q0, and should also comply with the requirements of the Road Traffic Safety Law of the People's Republic of China. Driving at the flow rate D < D2, X > X0 can ensure that the headway distance is greater than the minimum safe distance at the specified speed V, improve driving safety, and reduce the occurrence of traffic accidents.

[0040] 5. Road radar monitoring measures the speed of each vehicle and records the time t i , according to formula (2) The design program automatically performs probability statistics to find the mathematical mean μ of the flow velocity. Calculate the variance σ of distribution function using mathematical statistics method 2 ; μ、σ 2 The value is the actual traffic capacity observed on this road; the actual μ, σ 2 Based on the data, the D1 and D2 values ​​are determined by optimization and adjustment. In the early stage of road construction, the D1 and D2 values ​​can also be determined first according to the design status. The flow rate index indicates the minimum and maximum values ​​of the road capacity (flow rate) on the road speed sign. i (D1~D2) driving reduces the distribution variance σ 2 , optimizes and regulates human driving behavior, improves the actual traffic capacity of roads, reduces congestion, improves driving safety and reduces traffic accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a system structure block diagram of the present invention;

[0042] Figure 2 This is a schematic diagram of the vehicle passing through section A of the present invention;

[0043] Figure 3 V of the present invention i﹢1 With V i Schematic diagram of the angle a. DETAILED DESCRIPTION

[0044] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0045] like Figure 1 As shown, a traffic flow parameter-based flow velocity prompting system of the present invention comprises:

[0046] A vehicle speed signal collection unit is used to obtain vehicle speed data;

[0047] Collect the front and rear distance signal units of the front and rear vehicles to measure the distance from the cab to the rear of the front vehicle;

[0048] Processing, analysis and calculation unit, used to receive speed and distance to calculate D and X0;

[0049] Output command unit, used to issue instructions to the driver according to the calculation results of D and X0;

[0050] The driving status prompt unit is used to remind the driver to perform corresponding flow speed operations.

[0051] A flow velocity prompting method based on traffic flow parameters, comprising:

[0052] Step S1, according to the definition of flow rate and speed, a new traffic flow parameter flow rate is proposed, and its expression is D=Vq;

[0053] The relationship between the traffic flow velocity D, flow rate q, and speed V is:

[0054] D=Vq

[0055] Where q is the traffic volume or flow (Veh / h); V is the location speed (km / h). D is the flow (Veh km / h 2 ).

[0056] A new traffic flow parameter velocity is proposed, and its expression is D = Vq;

[0057] D=Vq(1)

[0058] Where D represents the flow velocity of the vehicle passing through the observation section or location at a speed of V at time t, and i represents it as:

[0059] D i =V i q i or

[0060] Among them, V i is the location speed, D i is the location flow velocity.

[0061] The measurement method is as follows: at section A, start timing at section A, t0 = 0, and after a period of time t i , record the number of vehicles passing through N i , and use a tachometer to record the location speed V i , a counting sensor is set on the monitoring recorder on the road, that is, recording N i and t i Simultaneously record Vi , use V i Location speed, t i 、V i Easy to measure, avoid K i Not easy to measure.

[0062] Step S2, take section A as the observation point (such as Figure 2 As shown), observe the actual data of flow rate D, and find The mean value is calculated by mathematical statistics method. 2 . n is a natural number. According to μ, σ 2 Optimize the design of road capacity and optimize the determination of D1 and D2 values, where D1 is the minimum flow rate and D2 is the maximum flow rate. You can also try to determine the D1 and D2 values ​​based on the design status at the beginning of road construction. Mark D1 and D2 on road signs.

[0063] Starting from the physical meaning of flow velocity, traffic status can be divided into two parts: free flow state and non-free flow state. The traffic flow characteristics of non-free flow state: the front vehicle or overtaking or ramp into the main road or reverse process affects the speed of the rear vehicle or changes the traffic flow state of the rear vehicle; if it reaches saturation, such as 2400veh / h / 1n or a certain value, it is a saturated state. At this time, the flow rate is a saturated flow rate q0. In this state, the maximum density corresponding to any speed satisfies VK0=q0, and the K0 value is a saturated density; the corresponding head spacing is a saturated spacing X0, that is, the minimum safe distance at this speed, and the corresponding speed is a saturated speed represented by V0, which can also be expressed by critical density or critical speed. D i There is no additive property, but the average value can be calculated as follows: use The average flow rate can reflect the actual state of traffic flow rate, where D is a countable, finite, discontinuous parameter and n is a natural number.

[0064] According to the flow rate calculation formula (2), make is the average headway time, Ruodang For N i Car and N n－1 The headway time of the vehicle is t i ,but:

[0065]

[0066] Where D i Unit: Vehkm / h 2 , t i Unit: S / veh;

[0067] Same reason is the average headway, if N i With N i－1 Headroom X i , (unit: m / Veh) then:

[0068]

[0069] Formula (4) D i With V i 2 Proportional to X i Inversely proportional, when driving on the road, there is a speed limit, the speed has an upper limit, and the headway has a minimum value, then has a maximum value;

[0070] Congestion speed V<20km / h, Dcongestion=20×1600=32kVehKm / h 2 , D max =(80~120)×(1800~2400)=(144~288)kVehkm / h 2 , use D max Using flow velocity as a measure of road capacity avoids the contradiction that large flow volume and possibly slow speed are used as the basis for road capacity.

[0071] Step S3, using the flow rate D parameter, optimize and regulate human driving behavior D1<D<D2, X>X0. D1 is the minimum flow rate on the road, D2 is the maximum flow rate on the road. Dmax is the road capacity index. X0 is the saturated headway.

[0072] like Figure 3 As shown in the figure, the flow rate is calculated by taking section A of the road as the observation point. Stable value, according to this phenomenon, if q i =V i K i =q i﹢1 =V i﹢1 K i﹢1 , then we understand that car i leaves and car i+1 enters, and i and i+1 are the front and back relationship of the vehicle space;

[0073] Flow velocity iteration equation: velocity and headway on a one-dimensional road section under non-free flow conditions, The formula for speed and headway distance is It is deduced that:

[0074]

[0075] like and There is an angle a, such as Figure 2As shown, then:

[0077]

[0079] Formula (6) is cosa squared, indicating that the angle between the ramp and the main road is sensitive to the flow velocity and has a greater impact, indicating that the angle of the leading vehicle overtaking is sensitive to the flow velocity of the following vehicle.

[0080] Step S4, based on steps S1 to S3, a traffic flow parameter flow speed prompt system is established.

[0081] The traffic flow parameter velocity prompting system of the present invention is based on formula (4): Traffic flow parameter flow speed prompt system extracts speed information from the car and uses radar or laser to measure the distance S to the front car in meters, X i =S+S1, S is the distance from the cab to the rear of the vehicle in front, S1 is the distance from the rear of the vehicle in front to the front window of the cab. The reminder system is installed on the front window of the cab. Formula (4) Automatic calculation is performed. When the flow rate is lower than a certain value, the flow rate prompt system reminds the driver to increase the flow rate. First look at the speed meter. Low flow rate generally means low speed. Acceleration is used to increase the speed. When the speed is increased, the distance between the front of the vehicle will naturally decrease. At the same time, the speed will increase the flow rate. The combined effect of the flow rate is rapidly increased. If the flow rate is high, braking is used to reduce the speed. When the speed is reduced, the distance between the front of the vehicle will naturally increase. The flow rate drops rapidly. Or a fully automatic flow rate control system is used to convert the driving power to control.

[0082] In actual application, when When D1 is at the minimum value and D2 is at the maximum value, the green light is on. i >D2(such as 264kVehkm / h 2 ) or the headway X<X0, the red light is on. It reminds that the flow rate is too high or the headway is too small, and the traffic flow parameter flow rate prompt system emits a warning sound. If D i Lower than D1 (such as 160kVehkm / h 2 ), the traffic flow parameter velocity prompt system emits a prompt sound, telling you that the velocity is too low and needs to be increased.

[0083] Different D1 and D2 reminder systems are set on highways and expressways, using instrument traffic lights and audio functions to remind. This can increase the flow rate and ensure that vehicles travel at a higher flow rate during holidays. This improves the road capacity and also avoids overtaking due to large vehicle intervals, which reduces the speed.

[0084] The current road has a maximum speed limit Vmax, and there is no requirement to ensure that it is greater than the minimum safe headway Xmin, which is easy to cause traffic accidents. It is difficult and unscientific to set X alone. Because X is related to V, the larger the V, the larger the X, and the smaller the V, the smaller the X. X is a function of V. Using the flow rate D(V 2 / X) can overcome this problem. When D is constant, dX 2 / dV 2 =2000 / D>0, indicating that the rate of change of X to V dX / dV increases with the increase of V, and the safety distance X increases rapidly with the increase of speed V. D=1000V 2 / X model guides driving more safely. For double insurance, the prompt system sets the saturated headway X0, press X i >X0 prompts driving. X0 is calculated according to the basic free flow speed and basic traffic capacity of the basic road section in the industry standard JTD-2017 "Highway Route Design Specifications" of the People's Republic of China, that is, the saturated flow q0, X0 = 1000V0 / q0, and should also comply with the requirements of the Road Traffic Safety Law of the People's Republic of China. Driving according to the flow rate D < D2, X i >X0 driving can ensure that the head distance is greater than the minimum safe distance at the specified speed V, thereby improving driving safety and reducing traffic accidents.

[0085] On the lane, the traffic flow parameter flow speed prompt system is used to avoid the interval between cars being too large or too small. The flow speed can be combined with the navigation system, and the flow speed data can be displayed on the display screen of the navigation system. The navigation system can obtain the speed parameter and then measure the X i value, and use The flow rate of each vehicle can be identified by calculation. In today's congested and blocked conditions, navigation generally makes a general and qualitative identification. The flow rate can be used to quantitatively distinguish between smooth, congested or blocked conditions.

[0086] At night or in rainy, snowy or foggy days, driving according to the level specified by the flow rate prompt system ensures safety and a certain driving speed.

[0087] At the intersection, the traffic flow parameter flow speed prompt system is set up i →0 (If the parking state can be set to X i =6.5m) to control and adjust the parking distance to achieve basically the same distance, which can shorten the distance between vehicle heads and increase flow rate.

[0088] The traffic flow parameter and speed prompt system on the road can be used for driving in road following mode.

[0089] If some vehicles do not follow the traffic flow parameter flow speed prompt system during use, or if the speed of a vehicle in a lane slows down due to some unexpected reasons, the iterative equation will affect the flow speed D of the next vehicle. i+1 decline.

[0090] Slowing D i+1 It will spread upstream and slow down, but due to the traffic flow parameter flow speed prompt system will automatically follow the V i Speed ​​prompt: adjust the distance to make the flow rate stable and restore the original flow rate D i The traffic flow parameter and velocity prompt system has this function, which enables it to achieve a new balance of traffic flow. When the sudden cause is eliminated, the traffic flow parameter and velocity prompt system will automatically prompt to increase the velocity D i , according to the original design flow rate D i Adjust the headway and speed to achieve a new traffic flow balance and initial flow rate state. If the traffic flow parameter flow rate prompt system is upgraded to an intelligent flow rate control system, the intelligent flow rate control system has a self-adjusting drive function.

[0091] The traffic flow parameter flow speed prompt system can also temporarily shut down its function according to the actual traffic environment.

[0092] Road radar monitoring measures the speed of each vehicle and records the time t i , according to formula (2) The design program automatically performs probability statistics to find the mathematical mean μ of the flow velocity. Calculate the variance σ of distribution function using mathematical statistics method 2 . μ、σ 2 The value is the actual traffic capacity of this road. 2 The D1 and D2 values ​​can also be determined by optimizing the value adjustment. In the early stage of road construction, the D1 and D2 values ​​can be first determined according to the design status. The flow rate index indicates the minimum and maximum values ​​of the road capacity (flow rate) on the road speed sign. i (D1~D2) driving reduces the distribution variance σ 2 , optimized and standardized human driving behavior, improved the actual road capacity, reduced congestion, and reduced traffic accidents.

[0093] In summary, the present invention uses a new traffic flow parameter velocity expression (model) to avoid the drawbacks of traffic flow parameters that have no direct correspondence between flow and speed. When in a non-free flow state, there is a correspondence between flow velocity and speed. K is difficult to measure. Flow velocity is an indicator of road capacity.

[0094] Traffic congestion or dissipation judgment inequality △D>0 means congestion, △D<0 means dissipation.

[0095] In non-free flow conditions, the velocity iteration equation

[0096] On highways, expressways and other roads, using traffic flow parameter velocity prompt system or intelligent velocity control system to drive at a velocity D between D1 and D2 (X>X0) can improve road capacity and reduce congestion (D>D1). Improve driving safety and reduce traffic accidents (D<D2, X>X0). It meets people's high-speed driving needs and brings high benefits to society.

[0097] The present invention optimizes and regulates human driving behavior, improves road traffic capacity, reduces congestion, and reduces traffic accidents.

[0098] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. A method for prompting flow velocity based on traffic flow parameters, characterized in that: include: Step S1, according to the definition of flow rate and speed, a new traffic flow parameter flow rate is proposed, and its expression is D=Vq; Step S2: Take the section A of the road as the observation point, observe the actual data of the flow velocity D, and calculate The mean value is calculated by mathematical statistics method. 2 , n is a natural number, according to u, σ 2 Optimize the design of road traffic capacity, optimize the determination of D1 and D2 values, where D1 is the minimum flow rate and D2 is the maximum flow rate. In the early stage of road construction, first try to determine the D1 and D2 values ​​according to the design status, and mark D1 and D2 on the road signs; Step S3, using the flow rate D parameter to optimize and regulate human driving behavior D1<D<D2; X>X0, D1 is the minimum flow rate on the road, D2 is the maximum flow rate on the road, Dmax is the road capacity index; X0 is the saturated headway; Step S4, based on steps S1 to S3, a traffic flow parameter flow speed prompt system is established.

2. The method for prompting flow speed based on traffic flow parameters according to claim 1, characterized in that: In step S1, according to the definition of flow rate, a new traffic flow parameter flow rate is proposed, which is represented by the letter D: D=Vq (1) Where D represents the flow velocity of the vehicle passing through the observation section or location at a speed of V at time t, and i represents it as: Among them, V i is the location speed, D i is the location flow velocity.

3. The method for prompting flow speed based on traffic flow parameters according to claim 2 is characterized in that: The measurement method is as follows: at section A, start timing at section A, t0 = 0, and after a period of time t i , record the number of vehicles passing through N i , and use a tachometer to record the location speed V i , a counting sensor is set on the monitoring recorder on the road to record V i Record N at the same time i and t i , use V i Location speed, t i 、V i Easy to measure, avoid K i Not easy to measure.

4. The method for prompting flow velocity based on traffic flow parameters according to claim 1, characterized in that: In step S1, starting from the physical meaning of flow speed, the traffic state can be divided into two parts: free flow state and non-free flow state. The traffic flow characteristics of the non-free flow state are: The front vehicle or overtaking or ramp into the main road or reverse process affects the speed of the rear vehicle or changes the traffic flow state of the rear vehicle; if it reaches saturation, such as 2400veh / h / 1n or a certain value is a saturation state; at this time, the flow is a saturated flow q0, and the maximum density corresponding to any speed in this state satisfies VK0=q0, and K0 is a saturated density; the corresponding headway is a saturated spacing X0, that is, the minimum safe distance at this speed, and the corresponding speed is a saturated speed, represented by V0, which can also be expressed by critical density or critical speed, D i There is no additive property, but the average value can be calculated as follows: use The average flow rate can reflect the actual state of traffic flow rate, where D is a countable, finite, discontinuous parameter and n is a natural number.

5. The method for prompting flow speed based on traffic flow parameters according to claim 2, characterized in that: According to the flow rate calculation formula (2), make is the average headway time, Ruodang For N i Car and N n－1 The headway time of the vehicle is t i ,but: Where D i Unit: Vehkm / h 2 , t i Unit: S / veh; Same reason Average headway, if N i With N i－1 Headroom X i , (unit: m / Veh) then: Formula (4) D i With V i 2 Proportional to X i Inversely proportional, when driving on the road, there is a speed limit, the speed has an upper limit, and the headway has a minimum value, then has a maximum value; Congestion speed V<20km / h, Dcongestion=20×1600=32kVehKm / h 2 , D max =(80~120)×(1800~2400)=(144~288)kVehkm / h 2 , use D max Using flow velocity as a measure of road capacity avoids the contradiction that large flow volume and possibly slow speed are used as the basis for road capacity.

6. The method for prompting flow speed based on traffic flow parameters according to claim 1, characterized in that: Take section A as the observation point and calculate the traffic volume Stable value, according to this phenomenon, if q i =V i K i =q i﹢1 =V i﹢ 1K i﹢1 , then we understand that car i leaves and car i+1 enters, and i and i+1 are the front and back relationship of the vehicle space; Flow velocity iteration equation: velocity and headway on a one-dimensional road section under non-free flow conditions, The formula for speed and headway distance is It is deduced that: like and There is an angle a, then: Formula (6) is cosa squared, indicating that the angle between the ramp and the main road is sensitive to the flow velocity and has a greater impact, indicating that the angle of the leading vehicle overtaking is sensitive to the flow velocity of the following vehicle.

7. A traffic flow parameter-based velocity prompt system, characterized in that: include: A vehicle speed signal collection unit is used to collect vehicle speed data; Collect the front and rear distance signal units of the front and rear vehicles to measure the distance from the cab to the rear of the front vehicle; Processing, analysis and calculation unit, used to receive speed and distance to calculate D and X0; The output command unit issues commands to the driver according to the calculation results of D and X0; The driving status prompt unit is used to remind the driver to perform corresponding flow speed operations.

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