CN105133450A - Design method for road crossing turn-around region provided with center isolation guardrail - Google Patents

Abstract

The invention discloses a method for designing a U-turn area at a road intersection with a central isolation guardrail. The present invention includes: A) determining the traffic capacity calculation model of the left-turn and U-turn shared lane first, and B) determining the U-turn area position of the left-turn and U-turn shared lane. By analyzing the interaction mechanism of left-turn and U-turn traffic flow under different conditions, the invention establishes a traffic capacity calculation model for left-turn and U-turn shared lanes, and establishes a calculation method for the optimal location of the U-turn area with the goal of maximizing traffic capacity, which overcomes the The blindness of the current U-turn area setting improves the scientificity and practicality of the U-turn area setting. The invention can not only be used for optimizing and reforming the U-turn area of the current road crossing, but also has important guiding significance for the design and construction of the proposed road crossing.

Description

A Design Method for U-turn Area at Road Intersection with Central Isolation Guardrail

technical field

The invention relates to the field of traffic planning and design, in particular to a design method for a U-turn area at a road intersection with a central isolation guardrail.

Background technique

A road intersection with a central isolation guardrail refers to the section of the intersecting road and the center of the intersection entrance road where an isolation guardrail is set. The effective green time is the time displayed with the green light minus the lost time. The left-turn and U-turn shared lane capacity refers to the maximum number of vehicles that can pass through the shared lane within one hour under the current road, traffic, control and environmental conditions. The vehicle lane length refers to the space length including the length of the vehicle itself and the safe distance between the front and rear vehicles.

At present, there is still no reasonable and feasible method for the optimal location of the U-turn area at the intersection of urban roads, which are all set by traffic management personnel based on experience, resulting in obvious mutual interference between the left-turn traffic flow and the U-turn traffic flow during the passage, resulting in a waste of time and resources in the lane and reduced capacity.

After long-term investigation and research by the inventor, by analyzing the mutual influence mechanism of left-turn and U-turn traffic flow under different conditions, a traffic capacity calculation model of left-turn and U-turn shared lanes is established, and the maximum traffic capacity of the U-turn area is determined with the goal of maximizing traffic capacity. The optimal setting position makes the interaction between the left-turn traffic flow and the U-turn traffic flow the least, and the utilization rate of lane resources is the highest.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a method for designing a U-turn area at a road intersection with a central isolation guardrail.

The present invention comprises the following steps:

A) First establish the capacity calculation model for left-turn and U-turn shared lanes, specifically:

a) First determine the traffic flow characteristics of the left-turn and U-turn shared lanes

The traffic flow characteristics here include three parameters: the vehicle arrival rate d per unit time, the left-turn U-turn ratio λ, and the length of vehicle occupancy when queuing up at intersections l ₀ ;

The methods for determining the traffic flow characteristics of left-turn and U-turn shared lanes include the following two methods:

1) On-the-spot investigation to obtain data for calculating the traffic flow characteristics of left-turn and U-turn shared lanes

This is mainly for the optimization of existing road intersections. The data to be obtained include: the number of left-turning and U-turning vehicles arriving and passing through the shared lane for left-turning and U-turning during peak hours, and the intersection signal timing scheme;

Use the data obtained from the survey to calculate the proportion of left-turning and U-turning vehicles on the shared lane for left-turning and U-turning vehicles λ, the vehicle arrival rate d, and the length of each vehicle's occupancy when queuing up at intersections l ₀ ;

2) Analyze and predict, directly determine the traffic flow characteristics of left-turn and U-turn shared lanes

This is mainly for the proposed intersection, fully consider the surrounding traffic demand in the planning stage, and obtain the ratio λ of left-turn vehicles and U-turn vehicles on the left-turn and U-turn shared lane of the intersection, the vehicle arrival rate d, and the time of parking and queuing at the intersection The lane length l ₀ of each vehicle;

b) Then determine the design parameters of the intersection;

The intersection design parameters here include: the distance L ₁ between the parking line of the opposite entrance lane and the entrance parking line, the width H of the adjacent exit lane, the design vehicle speeds of each entrance of the intersection for going straight, turning left, and making a U-turn V _straight , V _{left Set} , set V, _set the length of the canalized section at the entrance of the intersection L ₂ , and the length of the left-turn waiting area L ₃ ;

There are two ways to obtain the design parameters of intersections:

1) On-the-spot investigation to obtain data for calculating intersection design parameters

Measure the distance L ₁ between the parking line of the opposite entrance lane and the entrance parking line, the number of adjacent exit lanes and the lane width H, the length L ₃ of the channelized section of the entrance at the intersection, and measure the speed of vehicles passing through the intersection with a speedometer;

2) Consult the intersection design scheme and directly obtain the intersection design parameters

c) Determine the intersection signal timing scheme;

The methods for obtaining the signal timing scheme at intersections include the following two methods:

1) On-the-spot investigation, recording the sequence of traffic flow, the duration of each stage, and the duration of the signal cycle c;

2) Consult the intersection design scheme, and directly obtain the detailed signal timing design scheme of the intersection;

d) Finally, establish the capacity calculation model of the left-turn and U-turn shared lane

The process of establishing the capacity calculation model of the left-turn and U-turn shared lane includes:

1) First analyze the reasons for the time loss of left-turn and U-turn shared lanes

The process of analyzing the time loss of the left-turn and U-turn shared lane: Since the U-turn area is set in the channelized section, when the U-turn vehicle first enters the shared lane and stops in the U-turn area, the subsequent left-turn vehicles can only follow and stop If the parking line cannot be reached (including the front-end parking line in the left-turn waiting area), then a "vacuum zone" will be formed between the U-turn area and the parking line. When the left-turn and U-turn green lights are on, turn left. It is necessary to wait for the U-turn vehicle to leave before starting from a position far away from the stop line, and the time for the left-turn vehicle to wait for the U-turn vehicle to leave and pass through the "vacuum zone" is the first type of lost time in the shared lane; in the second case, During the signal phase when left turns are prohibited and U-turns are allowed, when the queue length of left-turn vehicles exceeds the U-turn area, the normal passage of U-turn vehicles will be blocked, making the remaining green light time empty. This is the second type of lost time in shared lanes ; The reasons for the time loss of the shared lane are mainly classified into two categories, namely: the time loss caused by the U-turn vehicle blocking the left-turn vehicle and the time loss caused by the left-turn vehicle blocking the U-turn vehicle;

2) Secondly, the time loss calculation model under two types of situations is established

The process of establishing the time loss calculation model in two types of situations: First, analyze the time loss caused by the U-turn vehicle blocking the left-turn vehicle, which is equal to the clearing time of the last straight vehicle passing the U-turn gate in the previous stage, the vehicle start-up loss time, and the time lost by the U-turn vehicle. The sum of the time for the first left-turning vehicle blocked by the vehicle to pass through its "vacuum zone"; secondly, the time loss caused by the left-turning vehicle blocking the U-turn vehicle is analyzed, which is equal to the total duration of the signal phase minus the time from the left-turning red light in this phase. The time elapsed from the beginning of light to the time when the left-turn vehicles line up to block the U-turn;

3) Then determine the total lost time calculation model for left-turn and U-turn shared lanes

The process of calculating the total lost time of the left-turn and U-turn shared lanes: the time loss caused by the U-turn vehicle blocking the left-turn vehicle and the time loss caused by the left-turn vehicle blocking the U-turn vehicle include many situations, and each situation has its own corresponding probability and lost time, the mathematical expectation of the total lost time is the sum of lost times multiplied by their occurrence probabilities in all situations;

4) Finally, establish a capacity calculation model for left-turn and U-turn shared lanes

Here is the process of establishing the capacity calculation model for left-turn and U-turn shared lanes: subtract the total lost time from the unit transit time to obtain the effective transit time, divide the effective transit time by the transit time of standard vehicles per unit, and obtain the left-turn and U-turn shared lane the capacity of the lane;

B) Determine the U-turn area position of the left-turn and U-turn shared lane again, specifically:

a) First solve the traffic capacity of the left-turn and U-turn shared lane under different U-turn area positions

When the traffic characteristics of the left-turn and U-turn lanes and the intersection design parameters are known, let the U-turn area position take a value between ₀ and L2, and obtain the traffic capacity of the left-turn and U-turn shared lane under different U-turn area positions ;

b) Determine the location of the U-turn area of the left-turn and U-turn shared lane

Utilize the traffic capacity of the left-turn and U-turn shared lane under different U-turn area positions, draw the corresponding change curve of the traffic capacity of the left-turn and U-turn shared lane and the U-turn area position, so that the position with the largest traffic capacity is the best position .

In the process of calculating the traffic capacity of the left-turn and U-turn shared lane, the present invention establishes and simplifies the model according to the traffic flow characteristics of the lane, the design parameters of the intersection, and in combination with the actual operation characteristics of the intersection, and takes the maximum traffic capacity as The goal is to determine the best setting position of the U-turn area, so that the interaction between the left-turning traffic flow and the U-turning traffic flow is the least, and the utilization rate of lane resources is the highest.

Beneficial effects of the present invention:

1) when the present invention determines the optimal setting position of the U-turn area, it is based on the traffic flow characteristics of the lane and the design parameters of the intersection, and fully considers the conflict types that may occur in the middle of the actual operation, and establishes a model so that the setting of the U-turn area is more accurate. accurate and reasonable;

2) The present invention continues to use the previous vehicle arrival rate model and the setting form of the road intersection U-turn area with the central isolation guardrail, and initiates the position design method of the U-turn area, combining the intersection size, design speed and left-turn U-turn requirements, so that the establishment of The capacity calculation formula in the paper can more accurately describe the influence of the location of the U-turn area on the operating efficiency of the left-turn and U-turn shared lanes, and can better serve urban traffic planning and management.

Description of drawings

Fig. 1 is a schematic diagram of a plane intersection to which the present invention is applicable;

Fig. 2 is a schematic diagram of a signal timing scheme adopted in the present invention;

Fig. 3 is a schematic diagram of queuing at an intersection where a U-turn vehicle blocks the passage of a left-turn vehicle;

Fig. 4 is a schematic diagram of queuing at an intersection where left-turning vehicles block the passage of U-turning vehicles;

Fig. 5 is a flowchart of the method of the present invention.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing.

As shown in Fig. 1, Fig. 2, Fig. 3, Fig. 4 and Fig. 5, the steps of this embodiment include: first establishing the traffic capacity calculation model of the left-turn and U-turn shared lane, and then determining the U-turn area of the left-turn and U-turn shared lane Location.

A) In the process of determining the capacity calculation model of left-turn and U-turn shared lanes:

a) First determine the traffic flow characteristics of the left-turn and U-turn shared lanes, which include three parameters: the proportion of left-turn and U-turn vehicles on the left-turn and U-turn shared lane Occupied track length l ₀ ;

b) Then determine the design parameters of the intersection, including: as shown in Figure 1, the distance L ₁ between the stop line of the opposite entrance lane and the entrance stop line, the width H of the adjacent exit road, and the length L of the channelized section of the entrance at the intersection _2. The length of the left-turn waiting area L _3. The design vehicle speeds of going straight, turning left, and turning at each entrance of the intersection are V _straight , V _left , and V _adjustable . Here, L represents the location of the U-turn area to be solved, and h Indicates the width of the U-turn port, 6m is taken here;

c) Determine the signal timing scheme at the intersection, as shown in Figure 2, the U-turn signal is turned on at stage 2 and ends at stage 3, the signal cycle duration is c, and the duration of each stage is g ₁ , g ₂ , g ₃ , g ₄ ;

d) Finally determine the capacity calculation model of the left-turn and U-turn shared lane, the process includes:

1) First analyze the reasons for the time loss of the shared lane for left turns and U-turns:

The process of analyzing the reasons for the time loss of the shared lane for left turns and U-turns: As shown in Figure 3, since the U-turn area is set in the channelization section, when the U-turn vehicle first enters the shared lane and stops in the U-turn area, it will turn left Vehicle just can only follow parking but can't reach the stop line (comprising the front end stop line of the left-turn waiting area), so a "vacuum zone" will be formed between the U-turn area and the stop line. After the light is turned on, the left-turning vehicle has to wait for the U-turning vehicle to leave before starting from a position far away from the stop line, and the time for the left-turning vehicle to wait for the U-turning vehicle to leave and pass through the "vacuum zone" is the first type of lost time in the shared lane ; In the second case, as shown in Figure 4, in the signal stage 3 of prohibiting left turn and allowing U-turn, when the queue length of left-turn vehicles exceeds the U-turn area, the normal traffic of U-turn vehicles will be blocked, so that the remaining green light time becomes Empty, this is the second type of time loss in the shared lane; the reasons for the time loss in the shared lane are mainly attributed to two categories, namely: the time loss caused by the U-turn vehicle blocking the left-turning vehicle and the left-turning vehicle blocking the U-turning vehicle belt coming time loss;

2) Secondly, establish the time loss calculation model in various situations

The process of establishing the time loss calculation model in various situations:

21) First analyze the time loss caused by the U-turn vehicle blocking the left-turn vehicle, which is equal to: the clearing time of the last vehicle going straight through the U-turn gate in the previous stage Vehicle start-up loss time, generally 2s, the time it takes for the first left-turning vehicle blocked by the U-turn vehicle to pass through its "vacuum zone" (Note: n is the sum of the number of left-turn queuing vehicles on the distance L ₃ +L in the period of stage 2), that is, the lost time is

22) Secondly, analyze the time loss caused by the left-turning vehicle blocking the U-turn vehicle, which is equal to the total duration of stage 3 minus the time from the time when the left-turning red light turns on to the left-turning vehicle queuing up to block the U-turn entrance;

Assume that the total duration of stage 3 is g ₃ , and arrive within t(0<t≤g ₃ ) seconds left-turning vehicle, the lost time at this time is

Y _2t =g ₃ -t

3) Then determine the total lost time calculation model for left-turn and U-turn shared lanes

31) First determine the time loss calculation model caused by the U-turn vehicle blocking the left-turn vehicle

Before the start of stage 2, the number n of left-turning vehicles queuing on section L ₃ +L ranges from 0 to x′ (x′ is The maximum value of the quotient, that is, the maximum carrying capacity of L ₃ +L segment), then the probability calculation formula in this case is:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}}{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}$

The calculation model of the time loss caused by the U-turn vehicle blocking the left-turn vehicle is

${\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\frac{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; L</span>}}{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}}{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; no</span>}}$

32) Next, determine the time loss calculation model caused by the left-turning vehicle blocking the U-turning vehicle

For the period of stage 3, find the time to arrive within t seconds The probability of a left-turning vehicle: According to the assumption that the vehicles are evenly distributed, then k left-turning vehicles correspond to A U-turn car, at this time the problem is transformed into:

Find the total number of vehicles arriving within t seconds as The probability According to the current research results, the arrival of vehicles obeys the Poisson distribution, and the total number of vehicles arriving within t seconds is The probability of

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; m</span>}}^{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; m</span>}}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; !</span>}$

Where m=d·t, represents the average number of vehicles arriving within the counting interval t;

Then the calculation model of the time loss caused by the left-turning vehicle blocking the U-turning vehicle is

${\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>$

33) Then determine the total lost time calculation model for left-turn and U-turn shared lanes

The total lost time of the left-turn and U-turn shared lane is the sum of the lost time in the two cases, and the calculation model of the total lost time is

Y=Y ₁ +Y ₂

4) Finalize the capacity calculation model for left-turn and U-turn shared lanes

The effective passage time is obtained by subtracting the lost time in the unit passage time from the unit passage time, and the effective passage time is divided by the passage time of a single vehicle to obtain the traffic capacity of the lane.

Among them, t _saturation represents the saturated headway of continuous traffic flow, that is, the transit time of a single vehicle here.

B) Determine the location of the U-turn area of the left-turn and U-turn shared lane

a) First solve the traffic capacity of the left-turn and U-turn shared lane under different U-turn area positions

When the traffic characteristics of the left-turn and U-turn lanes and the intersection design parameters are known, let the U-turn area position take a value between ₀ and L2, and obtain the traffic capacity of the left-turn and U-turn shared lane under different U-turn area positions ;

b) Determine the location of the U-turn area of the left-turn and U-turn shared lane

Utilize the traffic capacity of the left-turn and U-turn shared lane under different U-turn area positions, draw the corresponding change curve of the traffic capacity of the left-turn and U-turn shared lane and the U-turn area position, so that the position with the largest traffic capacity is the best position .

This embodiment provides a kind of traffic capacity calculation formula for left-turn and U-turn shared lanes, and solves the calculation method for the optimal location of the U-turn area at the intersection of road intersections with central isolation guardrails, overcomes the blindness of the current U-turn area setting, and improves It improves the utilization rate of road resources and has a high use value. It should be pointed out that those skilled in the art can make some improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims (5)

1. a road intersection U-turn area design method that central isolation guardrail is set, it is characterized in that the concrete steps of this method are: Step A) First establish the capacity calculation model of the left-turn and U-turn shared lanes; Step B) Determine the location of the U-turn area of the left-turn and U-turn shared lane; The step A) specifically includes the following steps: a) First determine the traffic flow characteristics of the left-turn and U-turn shared lanes; b) Then determine the design parameters of the intersection; c) Re-determine the intersection signal timing scheme; d) Finally, establish the capacity calculation model of the left-turn and U-turn shared lane, specifically: 1) First analyze the reasons for the loss of time in shared lanes for left turns and U-turns; 2) Secondly, establish the lost time calculation model in various situations; 3) Then determine the total lost time calculation model for left-turn and U-turn shared lanes; 4) Finally, establish a capacity calculation model for left-turn and U-turn shared lanes; The step B) specifically includes the following steps: a) First solve the traffic capacity of the left-turn and U-turn shared lane under different U-turn area positions; b) Then determine the location of the U-turn area of the left-turn and U-turn shared lane. 2. The method for designing a U-turn area at a road intersection according to claim 1, characterized in that: in the step A): The data to be obtained in step a) include: vehicle arrival rate d per unit time, left-turn U-turn ratio λ , and vehicle lane length l ₀ when queuing up at intersections; Step b) The data to be obtained include: the distance L ₁ between the stop line at the opposite entrance and the stop line at the entrance, the width H of the adjacent exit lane, the design speeds V for going straight, turning left, and making a U-turn in the intersection V _straight , V _left , V _{are adjusted} , the length of the channelized section of the entrance at the intersection is L ₂ , and the length of the left-turn waiting area is L ₃ ; The data to be obtained in step c) includes: the sequence of traffic flow, the duration of each signal phase g ₁ , g ₂ , g ₃ , g ₄ , and the duration c of the signal cycle. 3. The method for designing a road intersection U-turn area according to claim 1, characterized in that: the step d) of the step A) specifically includes: 1) First analyze the reasons for the time loss of left-turn and U-turn shared lanes; The process of analyzing the time loss of the left-turn and U-turn shared lane: Since the U-turn area is set in the channelized section, when the U-turn vehicle first enters the shared lane and stops in the U-turn area, the subsequent left-turn vehicles can only follow and stop If the stop line cannot be reached, a "vacuum zone" will be formed between the U-turn area and the stop line. The position starts to start, and the time for the left-turning vehicle to leave and pass through the "vacuum zone" is the first type of lost time in the shared lane; in the second case, in the third signal phase when the left-turn is prohibited and the U-turn is allowed, When the queue length of left-turn vehicles exceeds the U-turn area, it will block the normal passage of the U-turn vehicles, making the remaining green light time vacant. This is the second type of lost time in the shared lane; the reasons for the loss of time in the shared lane are mainly attributed to There are two categories, namely: the time loss caused by the U-turn vehicle blocking the left-turning vehicle and the time loss caused by the left-turning vehicle blocking the U-turn vehicle; 2) Secondly, the time loss calculation model under two types of situations is established; The process of establishing the time loss calculation model in two types of situations: First, analyze the time loss caused by the U-turn vehicle blocking the left-turn vehicle, which is equal to the clearing time of the last straight vehicle passing the U-turn gate in the previous stage, the vehicle start-up loss time, and the time lost by the U-turn vehicle. The sum of the time for the first left-turning vehicle blocked by the vehicle to pass through its "vacuum zone"; secondly, the time loss caused by the left-turning vehicle blocking the U-turn vehicle is analyzed, which is equal to the total duration of the signal phase minus the time from the left-turning red light in this phase. The time elapsed from the beginning of light to the time when the left-turn vehicles line up to block the U-turn; 3) Then determine the total lost time calculation model for left-turn and U-turn shared lanes; The process of calculating the total lost time of the left-turn and U-turn shared lanes: the time loss caused by the U-turn vehicle blocking the left-turn vehicle and the time loss caused by the left-turn vehicle blocking the U-turn vehicle include many situations, and each situation has its own corresponding probability and lost time, the mathematical expectation of the total lost time is the sum of lost times multiplied by their occurrence probabilities in all situations; 4) Finally, establish a capacity calculation model for left-turn and U-turn shared lanes; Here is the process of establishing the capacity calculation model for left-turn and U-turn shared lanes: subtract the total lost time from the unit transit time to obtain the effective transit time, divide the effective transit time by the transit time of standard vehicles per unit, and obtain the left-turn and U-turn shared lane Lane capacity. 4. The design method for U-turn area at road intersection according to claim 1, characterized in that: step a) in the step B) is specifically: the traffic characteristics of the left-turn and U-turn lanes, and the design parameters of the intersection are known In this case, let the position of the U-turn area take a value between 0 and L ₂ to obtain the traffic capacity of the left-turn and U-turn shared lane under different U-turn area positions. 5. The method for designing a U-turn area at a road intersection according to claim 1, characterized in that: step b) in the step B) is specifically: use the obtained left-turn and U-turn shared lanes under different U-turn area positions The traffic capacity of the left-turn and U-turn shared lanes is plotted corresponding to the change curve of the traffic capacity of the left-turn and U-turn area and the position of the U-turn area, so that the position with the largest traffic capacity is the best setting position.