| CPC G08G 1/0145 (2013.01) [G08G 1/0129 (2013.01); G08G 1/052 (2013.01); G08G 1/123 (2013.01)] | 3 Claims |
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1. A method for traffic flow control considering a bus stop in a connected environment, wherein the method is applied to a road with two lanes in one direction and a bus stop is provided in a first lane, and the method comprises the following operations;
1, when a bus travels in the first lane, a sum of a distance traveled by an upstream vehicle under the influence of a bus when the bus is in a process of stopping toward the bus stop and a speed of the bus is lower than a traffic flow speed is taken as a first distance; and a distance traveled by the bus when the bus is in a process of leaving the bus stop and the speed of the bus accelerates to the traffic flow speed is taken as a second distance; and a sum of the first distance and the second distance is taken as a length L of an influence region of the bus stop;
2, the length L of the influence region of the bus stop is calculated by using an equation (1);
L=Lup+Ldown (1)
wherein Lup denotes an influence distance of the bus on traveling of the upstream vehicle in a process of decelerating and stopping at the bus stop to resuming a uniform speed, i.e., an after-effect influence distance of the bus, and is obtained by an equation (2); and Ldown denotes a distance traveled by the bus in a process of leaving the bus stop to the uniform speed, i.e., a downstream influence distance of the bus, and is obtained by an equation (5);
 wherein νf denotes a free flow speed on the road with two lanes in one direction, and νs denotes a starting speed of the bus; η1 denotes a standardized density of road traffic when the bus does not decelerate and is obtained by an equation (3); and td denotes a predicted stop time of the bus and is obtained by an equation (4);
 in the equation (3), k1 denotes a traffic density of the road traffic when the bus does not decelerate, and ke denotes a traffic density when congestion occurs on the road with two lanes in one direction;
in the equation (4), a1, a2, . . . ap denote p regression coefficients, β1, . . . βq denote q sliding coefficients; td−1, td−2, . . . td−p denote p historical stop times of the bus, and εd, εd−1, . . . εd−q denote q white noise sequences;
 wherein νb denotes a speed at which the bus resumes the uniform speed after leaving the bus stop, and ag denotes acceleration of the bus;
3, a rectangular region formed by the length L of the influence region and a width of the road with two lanes in one direction is taken as the influence region, the bus stop is taken as an origin of the influence region, a traveling direction of the bus is taken as a positive direction of an x-axis, an x-axis horizontal coordinate of a distance Lup between the origin and an upstream road section as xLup, and an x-axis horizontal coordinate of a distance Ldown between the origin and a downstream road section is taken as xLdown, thereby dividing the influence region into three subregions;
wherein a first subregion is a rectangular region in the first lane with a central position of the bus as a start point and the xLdown as an end point;
a second subregion is a rectangular region in the first lane with the central position of the bus as a start point and the xLdown as an end point;
a third subregion is a rectangular region in a second lane with the xLup as a start point and the xLdown as an end point is;
4, a vehicle position, a vehicle speed, and vehicle acceleration in each of the three subregions within the influence region of the bus stop at time t are obtained using an intelligent connected roadside facility;
5, a lane changing pressure of an nth subregion at the time t is calculated using an equation (6), wherein n=1, 2, 3;
 wherein cn (t) denotes the lane changing pressure of the nth subregion at the time t, Kn,pre (t) denotes a density pressure of the nth subregion at the time t, and νn,pre(t) denotes a speed pressure of the nth subregion at the time t; λ1 and λ2 denote regulation parameters, kn (t) denotes a traffic density of the nth subregion at the time t, and km denotes a traffic density of a maximum traffic volume when vehicles travel normally on the road with two lanes in one direction; νn(t) denotes an average speed of all vehicles in the nth subregion at the time t; and Δt denotes a time interval;
6, a lane changing pressure difference ΔCr,r+1(t) between an rth subregion at the time t and an (r+1)th subregion at the time t is calculated by using an equation (7), thereby obtaining lane changing pressure differences {ΔCr,r+1(t)|r=1,2} of all the subregions;
ΔCr,r+1(t)=cr(t)−cr+1(t) (7)
wherein cr(t) denotes the lane changing pressure of the rth subregion at the time t, cr+1(t) denotes the lane changing pressure of the (r+1)th subregion at the time t, and r=1, 2;
7, two subregions having the larger absolute values of the lane changing pressure differences are selected from the lane changing pressure difference {ΔCr,r+1(t)|r=1,2} of all subregions to be prioritized for lane changing:
whether ΔCr,r+1(t)>0 is valid is determined, if ΔCr,r+1(t)>0 is valid, operation 7.1 is performed; otherwise, operation 10 is performed;
7.1, whether |ΔCr,r+1(t)>θ is valid is determined, and if |ΔCr,r+1(t)|>θ is valid is valid, operation 7.2 is performed; otherwise, lane changing of the vehicles within the influence region of the bus stop is prohibited, and operation 13 is performed; wherein θ denotes a lane changing threshold;
7.2, a count of vehicles Nr→r+1(t) that are allowed to transfer from the rth subregion to the (r+1)th subregion is calculated by using an equation (8);
 wherein Nr(t) denotes a count of vehicles in the rth subregion at the time t, and Lr(t) denotes a length of the rth subregion at the time t; Nr+1(t) denotes a count of vehicles in the (r+1)th subregion at the time t, and Lr+1(t) denotes a length of the (r+1)th subregion at the time t;
8, an ith vehicle in the rth subregion within the influence region of the bus stop at the time t is denoted as qir(t), a next vehicle in the (r+1)th subregion relative to the ith vehicle qir(t) in the rth subregion is denoted as qj+1r+1(t), and a previous vehicle in the (r+1)th subregion relative to the ith vehicle qir(t) in the rth subregion is denoted as qjr+1(t);
8.1, whether the ith vehicle qir(t) in the rth subregion at the time t satisfies a safety lane changing condition in an equation (9) is determined; if the ith vehicle qir(t) in the rth subregion at the time t satisfies the safety lane changing condition in the equation (9), the ith vehicle qir(t) is added to a lane changing set Pr→r+1(t); otherwise, it is indicated that the ith vehicle qir(t) cannot be transferred to the (r+1)th subregion at a safety lane changing spacing, and the ith vehicle qir(t) continues to travel in the rth subregion, thereby obtaining the lane changing set Pr→r+1(t);
 wherein xr,i(t) denotes a position horizontal coordinate of qir(t); xr+1,j(t) denotes a position horizontal coordinate of qjr+1(t); xr+1,j+1(t) denotes a position horizontal coordinate of qj+1r+1(t); Lr+1,j(t) denotes the safety lane changing spacing between qir(t) and qjr+1(t); Lr+1,j+1(t) denotes the safety lane changing spacing between qir(t) and qj+1r+1(t); νr+1,j(t) denotes a speed of qjr+1(t), and νr+1,j+1(t) denotes a speed of qj+1r+1(t); lveh denotes a length of a vehicle body; and Δtc denotes a duration of lane changing;
9, whether a count of vehicles Mr→r+1t≤Nr→r+1(t) in the lane changing set Pr→r+1(t) in the rth subregion within the influence region of the bus stop is valid is determined; if the count of vehicles Mr→r+1t≤Nr→r+1(t) in the lane changing set Pr→r+1(t) in the rth subregion within the influence region of the bus stop is valid, all the vehicles in the lane changing set Pr→r+1(t) in the rth subregion complete lane changing to the (r+1)th subregion, and operation 13 is performed; otherwise, a distance dr,i(t) between a vehicle qir(t) in the rth subregion and a previous vehicle qi−1r(t) is calculated by using an equation (10) to obtain distances between all the vehicles in the lane changing set Pr→r+1(t), and all the vehicles in the lane changing set Pr→r+1(t) are arranged in an ascending order based on the distances between all the vehicles to select top Nr→r+1(t) vehicles in the rth subregion with smallest spacings to fronts of the previous vehicles to complete lane changing to the (r+1)th subregion, and operation 13 is performed;
dr,i(t)=xr,i−1(t)−xr,i(t) (10)
wherein xr,i−1(t) denotes a position horizontal coordinate of the previous vehicle qi−1r(t) of the vehicle qir(t) in the rth subregion;
10, whether ΔCr,r+1(t)>θ is valid is determined, and if |ΔCr,r+1(t)|>θ is valid, operation 10.1 is performed; otherwise, the vehicles within the influence region of the bus stop are not allowed to change lanes, and operation 13 is performed;
10.1, a count of vehicles Nr→r+1(t) that are allowed to transfer from the (r+1)th subregion to the rth subregion is calculated by using an equation (11);
 11, the uth vehicle in the (r+1)th subregion within the influence region of the bus stop at the time t is denoted as qur+1(t), a latter vehicle in the rth region relative to the uth vehicle qur+1(t) in the (r+1)th subregion is denoted as qw+1r(t), and a previous vehicle in the rth subregion relative to the uth vehicle qur+1(t) in the (r+1)th subregion is denoted as qwr(t);
11.1, whether the uth vehicle qur+1(t) in the (r+1)th subregion at the time t satisfies a safety lane changing condition shown in an equation (12) is determined, if the uth vehicle qur+1(t) in the (r+1)th subregion at the time t satisfies the safety lane changing condition shown in the equation (12), the uth vehicle qur+1(t) is added to a lane changing set Pr+1→r(t); otherwise, it is indicated that the uth vehicle qur+1(t) cannot be transferred to the rth subregion at the safety lane change spacing, and the uth vehicle qur+1(t) continues to travel in the (r+1)th subregion, thereby obtaining the lane changing set Pr→r+1(t);
 wherein xr+1,u(t) denotes a position horizontal coordinate of qur+1(t); xr,w(t) denotes a position horizontal coordinate of qwr(t): xr,w+1(t) denotes a position horizontal coordinate of qw+1r(t); Lr,w(t) denotes the safety lane changing spacing between qwr(t) and qur+1(t); Lr,w+1(t) denotes the safety lane changing spacing between qw+1r(t) and qur+1(t); νr,w(t) denotes a speed of qwr(t), νr,w+1(t) denotes a speed of qw+1r(t), and Δtc denotes the duration of lane changing;
12, whether a count of vehicles Mr+1→rt≤Nr+1→r(t) in the lane changing set Pr+1→r(t) in the (r+1)th subregion within the influence region of the bus stop is valid is determined, and if the count of vehicles Mr+1→rt≤Nr+1→r(t) in the lane changing set Pr+1→r(t) in the (r+1)th subregion within the influence region of the bus stop is valid, all the vehicles in the lane changing set Pr+1→r(t) in the (r+1)th subregion complete lane changing to the rth subregion; otherwise, a distance dr+1,u(t) between the vehicle qur+1(t) in the (r+1)th subregion and the previous vehicle qu−1r+1(t) is calculated by using an equation (13) to obtain distances between all the vehicles in the lane changing set Pr+1→r(t), and all the vehicles in the lane changing set Pr+1→r(t) are arranged in an ascending order based on the distances between all the vehicles to select top Nr+1→r(t) vehicles in the (r+1)th subregion with smallest spacings to fronts of the previous vehicles to complete lane changing to the rth subregion;
dr+1,u(t)=xr+1,u−1(t)−xr+1,u(t) (13)
wherein xr+1,u−1(t) denotes a position horizontal coordinate of the previous vehicle qu−1r+1(t) of qur+1(t) in the (r+1)th subregion;
13, whether xbus(t)<xLdown is valid is determined, if xbus(t)<xLdown IS valid, t+Δt is assigned to t and the process returns to the operation 4; otherwise, the control process is ended, wherein xbus(t) denotes a position horizontal coordinate of the bus at the time t.
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