# Research on HOV Lane Priority Dynamic Control under Connected Vehicle Environment

Authors: Guiliang Zhou; Lina Mao; Pengsen Hu; Feng Sun; Xu Bao
Journal: Journal of Advanced Transportation
 (2020)

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## Abstract

The optimization of high-occupancy vehicle (HOV) lane management can better improve the efficiency of road resources. This paper first summarized the current research on HOV lane implementation and analyzed and identifies the threshold of setting road HOV lane dynamic control under the connected vehicle environment. Then, the HOV lane priority dynamic control process was determined, and the operating efficiency and energy consumption evaluation method was proposed. Moreover, a case study in Wuxi City, China, was carried out. The results showed that, after implementing the HOV lane priority dynamic control, the total mileage of road network vehicles was saved by 4.93%, the average travel time per capita was reduced by 4.27%, and the total energy-saving rate of road network travel was 21.96%.


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## Body

## 1. Introduction

The setting of the HOV lane can provide more space resources for high-occupancy vehicles to improve traffic operation efficiency. However, it met with great controversy at the beginning [1–3] because when the HOV lane was not fully utilized at the time, road space resources were wasted [4]; Pravin and Han [5] made a comprehensive comparison between the HOV lane and the ordinary lane set in California in the United States. After investigating the HOV lane capacity, traffic operating condition, and carpooling percentage, it was believed that, under the appropriate road and traffic conditions, HOV lanes can serve to improve the traffic capacity, but when a certain saturation is reached, frequent lane changes may cause a decline in capacity. Dahlgren [6] claimed that the HOV lane setting has a significant effect on reducing carbon dioxide and other greenhouse gas emissions. Gutierrez et al. [7–10] made a detailed comparative analysis of the implementation effects of toll lanes and HOV lanes and concluded different applicable conditions for toll lanes and HOV lanes. Chen [11] discussed the experience and lessons of HOV priority planning and application worldwide in detail and proposed the necessity and feasibility of introducing HOV priority into urban transportation planning in China. The conclusion shows that the development level and urban residential characteristics of intelligent transportation technology in China have provided the necessary conditions for the implementation of HOV lanes.Wang [12] put forward conceptual plans for carpooling priority based on the design experience of HOV schemes and pointed out that road, traffic, and urban land use functions are the key influencing factors of HOV lane setting in large cities. Bi [13] conducted an in-depth study on the carpooling rate model after the HOV lanes were set up and clarified the change law of the carpooling rate under the conditions of different passenger numbers for buses and HOV vehicles, thus proving the necessity and feasibility of setting HOV lanes in urban cities. Wu and Pan [14] analyzed and studied the relationship between the BRT lanes and HOV lanes on urban roads and the implementation strategy; some scholars also studied aspects such as operating efficiency and traffic conditions. The feasibility of HOV lane setting has been systematically studied [15–21], which provides a theoretical basis for the scientific and rational setting of HOV lanes. In summary, most of the previous studies focused on the feasibility of HOV lane setting, road conditions, and HOV lane static management. However, the dynamic control of HOV lanes based on real-time data is ignored. With the rapid development and improvement of information technology and Internet of Vehicles (IoV) technology, it is feasible to realize HOV lane dynamic control using real-time data for carpooling priority.


## 2. Threshold Determination for Setting HOV Lanes Priority Dynamic Control under Connected Vehicle Environment

HOV lanes provide the right of way for high-occupancy vehicles. It improves the operating efficiency of highways and attracts more people to carpool, thus reducing the number of trips by private cars with low occupancy, and alleviates the urban traffic congestion. At present, the use of HOV lanes mostly adopts the fixed scheme. With the development of data acquisition methods, it will be feasible to implement dynamic intelligent control over the HOV lanes under connected vehicle environment, which will realize the optimal management of infrastructure resources.In this section, in order to provide a basis for the dynamic control of HOV lanes with carpool priority, the threshold determination of introducing HOV lanes under connected vehicle environment was analyzed.


### 2.1. Speed-Volume Model

The BPR (Bureau of Public Roads) model shows the functional relationship between the travel time of road segments and the traffic load:(1)Tq=T01+αqcβ,where Tq refers to the travel time at flow q, T0 is the travel time when traffic volume q=0, C is the traffic capacity, and αandβ are model parameters.For the same traveler, the travel distance is a constant; therefore, equation (1) can be converted to the following equation:(2)Vq=V01+αq/cβ,where Vq refers to the traffic speed and V0 refers to the free-flow speed under the condition of mixed traffic of vehicles with different occupancy rates.The free-flow speed can be determined by the road grade, and its recommended value is shown in Table1.Table 1
Recommended value of free-flow speed for different grades of roads (km/h).
Road gradeExpresswayArterial roadCollector roadFree-flow speed60∼8050∼6040∼50In terms of the urban roads,V0 is mainly related to intersection spacing, stop time of stations, signal period duration, and green signal ratio, which can be calculated by the following equation:(3)V0=LL/Vf+d,where d refers to the average delay at intersections, L is the length of road segments, and Vf refers to the free-flow speed.


### 2.2. Speed-Volume Model Calibration

The least square method was used to calibrate the speed-volume model under the condition of mixed traffic and having HOV lane is as follows:(4)Vq=311+1.03q/c3.01.


### 2.3. Threshold for Introducing HOV Lane

For traffic travelers, the important indicator for evaluating travel quality is travel time, which heavily depends on the traffic condition. The traffic condition could be divided into two states: the ideal state and the actual state. Then, travel time is divided into ideal travel time and actual travel time as well. Actual travel time usually includes two parts: ideal travel time and ideal travel delay. The ideal travel time is only related to the travel distance and travel mode; that is, when the travel distance and mode are fixed, the ideal travel time is a fixed value, but the ideal travel delay will be determined by the traffic condition and will continue to increase as the traffic condition changes. The improvement and reduction of the traffic condition can effectively reflect the operating efficiency of the road network. This paper takes per capita delay as the evaluation index of road network operation efficiency. The threshold of introducing HOV lanes was investigated by minimizing per capita delay index.The per capita delay indexd′ could be calculated by using the following equation:(5)d′=qb·nb·db+qc·nc·dCqb·nb+qc·nc,where qb refers to the traffic volume of high-occupancy vehicles, nb represents the number of people in each occupancy vehicle, db refers to the delay for each high-occupancy vehicle, qc refers to the traffic volume of nonhigh-occupancy vehicles, nc represents the number of people in each nonoccupancy vehicle, and dc refers to the delay for each nonoccupancy vehicle.Per vehicle delayd can be calculated as follows:(6)d=LVq−LV0.According to the previous survey and data analysis, about 2/3 of the people who own private cars are willing to take carpool, and about 1/3 of the people owning private cars show reluctance to carpooling, as shown in Figure1.Figure 1
Bar graph of the carpooling willingness.It can be seen from Figure2 that most (50.3%) high-occupancy vehicles have two passengers, followed by one passenger (24.56%) and three passengers (24.26%). Only 0.89% high-occupancy vehicles have four passengers.Figure 2
Bar graph of different carpooling passenger numbers.Taking the bidirectional 6-lane road as an example, assumeqb=160veh/h and nb = 3, the threshold of setting HOV lanes priority dynamic control was determined as follows: firstly, substitute the traffic volumes into equations (3) and (4) to get the speed of high-occupancy and nonhigh-occupancy vehicles. Then, substitute the speeds into equation (6) to get the per vehicle delay for high-occupancy and nonhigh-occupancy vehicles. Finally, the per capita delay could be obtained by substituting the per vehicle delays into equation (5). Figure 3 shows the relationship between the per capita delay and the traffic volume before and after introducing HOV lane.Figure 3
Per capita delay under different traffic conditions atqb = 160 and nb = 3.If we change theqb from 160 to 180 vehicle per hour while other conditions remain the same, then the relationship between per capita delay and traffic volume is shown in Figure 4:Figure 4
Per capita delay under different driving conditions atqb = 180 and nb = 3.When the traffic volume of high-occupancy vehicles equals 160 vehicles per hour, it can be seen from Figure3 that the normal mixed traffic has less per capita delay than the traffic with HOV lane when traffic volume is less than 600 vehicles per hour. It means that it is unsuitable to set a HOV lane. However, when the traffic volume is greater than 600, a HOV lane should be implemented to reduce the per capita delay. In this case, traffic volume of 600 vehicles per hour is the threshold for setting the HOV lane. Similarly, it can be seen from Figure 4 that when the volume of high-occupancy vehicles equals 180 vehicles per hour, the threshold is 640 vehicles per hour. The thresholds for different traffic volumes of high-occupancy vehicles are presented in Table 2.Table 2
Thresholds for different traffic volumes of high-occupancy vehicles.
Traffic volumes of high-occupancy vehicles (veh/h)Number of passengers per high-occupancy vehicle (p/veh)Threshold (veh/h)150259235804566>4560160261536004582>4575180265036404628>4614200269336754662>4648


### 2.4. HOV Lane Priority Dynamic Control Process with Carpooling under Connected Vehicle Environment

After determining the threshold of setting HOV lanes, this paper selected carpooling ratio, degree of saturation (v/c), and average traffic speed as the indictors for HOV lane priority dynamic control.Taking a cycle at the downstream intersection of the road section as the time scale, the dynamic control flow chart is shown in Figure5.Step 1: using GPS, RFID, information transmission network, and other information collection technologies under the connected vehicle environment to collect the basic traffic information needed.Step 2: performing data preprocessing, data cleaning, data repair, and screening on the data collected in step 1.Step 3: uploading the processed data to the traffic information center.Step 4: displaying the traffic information and theoretically analyzing the demand for setting HOV lanes based on the carpooling ratio, degree of saturation (v/c), and average traffic speed.Step 5: setting the time scale as the signal cycle of the downstream intersection.Step 6: determining the number of passengers on high-occupancy vehicles (carpooling).Step 7: judging if the normal mixed traffic volume if greater than the threshold value. If yes, then HOV lanes only allow high-occupancy vehicles to access (setting HOV lanes). If no, HOV lanes open to all vehicles with different occupancy rates (removing HOV lanes).Step 8: repeating step 4 to step 7.Figure 5
Flow chart of HOV dynamic control process.


### 2.5. Evaluation of Implementing HOV Lane Priority Dynamic Control

Real-time traffic information such as number of passengers, travel time, vehicle location, and vehicle type can be obtained through connected vehicle technologies. In this paper, the reduction in per capita travel time and total travel mileage is selected as the evaluation indicator of the implementation of the HOV lane priority dynamic control.The main ideas are as follows: firstly, the real-time traffic operation condition of the road network in the mixed traffic state (before setting HOV lanes) is obtained: the number of passengers, travel time, and travel mileage. Secondly, based on the information above, the total travel mileage and travel time in the mixed traffic state can be calculated. Thirdly, theoretical analysis will be conducted to estimate the traffic operation condition assuming the HOV lanes were introduced and the total travel mileage and travel time of the new traffic state (after setting the HOV lanes) could be calculated as well. Finally, evaluate the effectiveness of implementing HOV lane priority dynamic control by vehicle mileage saving rate and reduction rate of per capita travel time consumption. The flow chart is shown in Figure6.Figure 6
The evaluation process of implementing HOV lane priority dynamic control.


#### 2.5.1. Traffic Information Acquisition in Mixed Traffic

Assume there arem sections in the road network and n cars in each section, then the vehicle mileage of the road network in the most initial operating state (mixed traffic) can be expressed as follows:(7)S0=∑j=0m∑i=0nSij0,where Sij0 is the mileage of the ith vehicle in the jth section of the road network and S0 is the total mileage of the vehicles.Then, the total travel time in the initial operating state could be calculated as follows:(8)PI0=Pa0∗Ta0+Pb0∗Tb0+Pc0∗Tc0,where PI0 is the total travel time, Pa0 is the number of noncarpooling travelers, Ta0 is the average travel time of noncarpooling travelers, Pb0 is the number of carpooling travelers, Tb0 is the average travel time of carpooling travelers,Pc0 is the number of public transportation travelers, and Ta0 is the average travel time of public transportation travelers.


#### 2.5.2. Transportation Mode Transfer

After the implementation of the HOV lane priority dynamic control, the trips of low-occupancy vehicles (private cars) in the road network will shift to high-occupancy vehicles (carpool). Through presurvey, the travel mode transfer function under different states is obtained, as shown in Table3.Table 3
The state functions of the transfer from private car to carpool.
StatePercentage increase in travel time (k)Transfer functionf(k)1<10%f(k) = −3.84k + 0.6293210%–30%f(k) = −1.179k + 0.3765330%–40%f(k) = −0.9735k + 0.4224440%–50%f(k) = −0.6045k + 0.08255>50%f(k) = −0.7168k + 0.0029


#### 2.5.3. Traffic Information Acquisition in Traffic with HOV Lanes

Assume there arem sections in the road network and n cars in each section, and then, the total vehicle mileage of the road network in the posterior operating state (after setting HOV lanes) can be expressed as follows:(9)S1=∑j=0m∑i=0nSij1,where Sij1 is the mileage of the i-th vehicle in the j-th section of the road network and S1 is the total mileage of the vehicles.Then, the total travel time in the v could be calculated as follows:(10)PI1=Pa1∗Ta1+Pb1∗Tb1+Pc1∗Tc1,where PI1 is the total travel time, Pa1 is the number of noncarpooling travelers, Ta1 is the average travel time of noncarpooling travelers, Pb1 is the number of carpooling travelers, Tb1 is the average travel time of carpooling travelers,Pc1 is the number of public transportation travelers, and Ta1 is the average travel time of public transportation travelers.


#### 2.5.4. Operating Efficiency Evaluation

The percentage reduction in total travel mileage can be expressed as follows:(11)M=∑j=0m∑i=0nSij0−∑j=0m∑i=0nSij1∑j=0m∑i=0nSij0.Similarly, the percentage reduction in per capita travel time can be expressed as follows:(12)p=PI0/Pao+Pbo+Pco−PI/Pa1+Pb1+Pc1PI0/Pao+Pbo+Pco.


#### 2.5.5. Energy Consumption Evaluation

Evaluation and comparison of road network energy consumption before and after HOV lane priority dynamic control is of great significance for the promotion and application of HOV lanes. According to the literature [22, 23], the energy consumption of different transportation modes in cities is summarized in Tables 4 and 5.Table 4
Energy consumption comparison of different types of vehicles.
Vehicle categoriesSedanPublic busTaxiPrivate carBus with multiple compartmentsBus with single compartmentFuel consumption (liter/100 km)10.21125.522.5Energy consumption (liter/(100 people∗km))7.346.780.410.73Energy consumption (kg standard coal/(100 people∗km)）8.527.870.480.85Note: coefficient for standard coal to fuel conversion = 0.7895 kg/liter × 1.4714 kg standard coal/kg = 1.1617 kg standard coal/liter.Table 5
Energy consumption comparison of different types of vehicles with different occupancies.
Vehicle categoriesSeating capacitiesEnergy consumption under different occupancies (liter/100 people∗km)25%50%75%100%SedanTaxi47.1593.7592.682.066Private car510.175.093.762.95Public busBus with multiple compartments801.280.700.510.41Bus with single compartment402.251.240.900.73According to the actual situation of the investigated city, the energy consumption of noncarpooling private car trips, carpooling private car trips, and public bus trips with single compartment was selected as 10.17 (25%), 3.67 (75%), and 1.24 (50%), respectively.The total energy-saving rate of road network can be calculated by the following equation:(13)H=αm·Pa0·Ja0·Qa0+βn·Pb0·Jb0·Qb0+γg·Pc0·Jc0·Qc0−αm·Pa1·Ja1·Qa1+βn·Pb1·Jb1·Qb1+γg·Pc1·Jc1·Qc1αm·Pa0·Ja0·Qa0+βn·Pb0·Jb0·Qb0+γg·Pc0·Jc0·Qc0,where H is the total energy-saving rate of road network;  αm is the energy consumption coefficient of noncarpooling trips, 10.17 × 10−5 L/p·m;  βn is the energy consumption coefficient of carpooling trips, 3.76 × 10−5 L/p·m;  γg is the energy consumption coefficient of public bus trips, 1.24 × 10−5 L/p·m; Ja0 is the average travel mileage of noncarpooling trips in the initial operating state (mixed traffic), m;  Jb0 is the average travel mileage of carpooling trips in the initial operating state (mixed traffic), m; Jc0 is the average travel mileage of public bus trips in the initial operating state (mixed traffic), m;  Qa0 is the number of vehicles of noncarpooling trips in the initial operating state (mixed traffic), veh;  Qb0 is the number of vehicles of carpooling trips in the initial operating state (mixed traffic), veh; Qc0 is the number of vehicles of public bus trips in the initial operating state (mixed traffic), veh; Ja1 is the average travel mileage of noncarpooling trips in the posterior operating state (after setting HOV lanes), m; Jb1 is the average travel mileage of carpooling trips in the posterior operating state (after setting HOV lanes), m; Jc1 is the average travel mileage of bus trips in the posterior operating state (after setting HOV lanes), m;  Qa1 is the number of vehicles of noncarpooling trips in the posterior operating state (after setting HOV lanes), veh;  Qb1 is the number of vehicles of carpooling trips in the posterior operating state (after setting HOV lanes), veh; and Qc1 is the number of vehicles of public bus trips in the posterior operating state (after setting HOV lanes), veh.


## 2.1. Speed-Volume Model

The BPR (Bureau of Public Roads) model shows the functional relationship between the travel time of road segments and the traffic load:(1)Tq=T01+αqcβ,where Tq refers to the travel time at flow q, T0 is the travel time when traffic volume q=0, C is the traffic capacity, and αandβ are model parameters.For the same traveler, the travel distance is a constant; therefore, equation (1) can be converted to the following equation:(2)Vq=V01+αq/cβ,where Vq refers to the traffic speed and V0 refers to the free-flow speed under the condition of mixed traffic of vehicles with different occupancy rates.The free-flow speed can be determined by the road grade, and its recommended value is shown in Table1.Table 1
Recommended value of free-flow speed for different grades of roads (km/h).
Road gradeExpresswayArterial roadCollector roadFree-flow speed60∼8050∼6040∼50In terms of the urban roads,V0 is mainly related to intersection spacing, stop time of stations, signal period duration, and green signal ratio, which can be calculated by the following equation:(3)V0=LL/Vf+d,where d refers to the average delay at intersections, L is the length of road segments, and Vf refers to the free-flow speed.


## 2.2. Speed-Volume Model Calibration

The least square method was used to calibrate the speed-volume model under the condition of mixed traffic and having HOV lane is as follows:(4)Vq=311+1.03q/c3.01.


## 2.3. Threshold for Introducing HOV Lane

For traffic travelers, the important indicator for evaluating travel quality is travel time, which heavily depends on the traffic condition. The traffic condition could be divided into two states: the ideal state and the actual state. Then, travel time is divided into ideal travel time and actual travel time as well. Actual travel time usually includes two parts: ideal travel time and ideal travel delay. The ideal travel time is only related to the travel distance and travel mode; that is, when the travel distance and mode are fixed, the ideal travel time is a fixed value, but the ideal travel delay will be determined by the traffic condition and will continue to increase as the traffic condition changes. The improvement and reduction of the traffic condition can effectively reflect the operating efficiency of the road network. This paper takes per capita delay as the evaluation index of road network operation efficiency. The threshold of introducing HOV lanes was investigated by minimizing per capita delay index.The per capita delay indexd′ could be calculated by using the following equation:(5)d′=qb·nb·db+qc·nc·dCqb·nb+qc·nc,where qb refers to the traffic volume of high-occupancy vehicles, nb represents the number of people in each occupancy vehicle, db refers to the delay for each high-occupancy vehicle, qc refers to the traffic volume of nonhigh-occupancy vehicles, nc represents the number of people in each nonoccupancy vehicle, and dc refers to the delay for each nonoccupancy vehicle.Per vehicle delayd can be calculated as follows:(6)d=LVq−LV0.According to the previous survey and data analysis, about 2/3 of the people who own private cars are willing to take carpool, and about 1/3 of the people owning private cars show reluctance to carpooling, as shown in Figure1.Figure 1
Bar graph of the carpooling willingness.It can be seen from Figure2 that most (50.3%) high-occupancy vehicles have two passengers, followed by one passenger (24.56%) and three passengers (24.26%). Only 0.89% high-occupancy vehicles have four passengers.Figure 2
Bar graph of different carpooling passenger numbers.Taking the bidirectional 6-lane road as an example, assumeqb=160veh/h and nb = 3, the threshold of setting HOV lanes priority dynamic control was determined as follows: firstly, substitute the traffic volumes into equations (3) and (4) to get the speed of high-occupancy and nonhigh-occupancy vehicles. Then, substitute the speeds into equation (6) to get the per vehicle delay for high-occupancy and nonhigh-occupancy vehicles. Finally, the per capita delay could be obtained by substituting the per vehicle delays into equation (5). Figure 3 shows the relationship between the per capita delay and the traffic volume before and after introducing HOV lane.Figure 3
Per capita delay under different traffic conditions atqb = 160 and nb = 3.If we change theqb from 160 to 180 vehicle per hour while other conditions remain the same, then the relationship between per capita delay and traffic volume is shown in Figure 4:Figure 4
Per capita delay under different driving conditions atqb = 180 and nb = 3.When the traffic volume of high-occupancy vehicles equals 160 vehicles per hour, it can be seen from Figure3 that the normal mixed traffic has less per capita delay than the traffic with HOV lane when traffic volume is less than 600 vehicles per hour. It means that it is unsuitable to set a HOV lane. However, when the traffic volume is greater than 600, a HOV lane should be implemented to reduce the per capita delay. In this case, traffic volume of 600 vehicles per hour is the threshold for setting the HOV lane. Similarly, it can be seen from Figure 4 that when the volume of high-occupancy vehicles equals 180 vehicles per hour, the threshold is 640 vehicles per hour. The thresholds for different traffic volumes of high-occupancy vehicles are presented in Table 2.Table 2
Thresholds for different traffic volumes of high-occupancy vehicles.
Traffic volumes of high-occupancy vehicles (veh/h)Number of passengers per high-occupancy vehicle (p/veh)Threshold (veh/h)150259235804566>4560160261536004582>4575180265036404628>4614200269336754662>4648


## 2.4. HOV Lane Priority Dynamic Control Process with Carpooling under Connected Vehicle Environment

After determining the threshold of setting HOV lanes, this paper selected carpooling ratio, degree of saturation (v/c), and average traffic speed as the indictors for HOV lane priority dynamic control.Taking a cycle at the downstream intersection of the road section as the time scale, the dynamic control flow chart is shown in Figure5.Step 1: using GPS, RFID, information transmission network, and other information collection technologies under the connected vehicle environment to collect the basic traffic information needed.Step 2: performing data preprocessing, data cleaning, data repair, and screening on the data collected in step 1.Step 3: uploading the processed data to the traffic information center.Step 4: displaying the traffic information and theoretically analyzing the demand for setting HOV lanes based on the carpooling ratio, degree of saturation (v/c), and average traffic speed.Step 5: setting the time scale as the signal cycle of the downstream intersection.Step 6: determining the number of passengers on high-occupancy vehicles (carpooling).Step 7: judging if the normal mixed traffic volume if greater than the threshold value. If yes, then HOV lanes only allow high-occupancy vehicles to access (setting HOV lanes). If no, HOV lanes open to all vehicles with different occupancy rates (removing HOV lanes).Step 8: repeating step 4 to step 7.Figure 5
Flow chart of HOV dynamic control process.


## 2.5. Evaluation of Implementing HOV Lane Priority Dynamic Control

Real-time traffic information such as number of passengers, travel time, vehicle location, and vehicle type can be obtained through connected vehicle technologies. In this paper, the reduction in per capita travel time and total travel mileage is selected as the evaluation indicator of the implementation of the HOV lane priority dynamic control.The main ideas are as follows: firstly, the real-time traffic operation condition of the road network in the mixed traffic state (before setting HOV lanes) is obtained: the number of passengers, travel time, and travel mileage. Secondly, based on the information above, the total travel mileage and travel time in the mixed traffic state can be calculated. Thirdly, theoretical analysis will be conducted to estimate the traffic operation condition assuming the HOV lanes were introduced and the total travel mileage and travel time of the new traffic state (after setting the HOV lanes) could be calculated as well. Finally, evaluate the effectiveness of implementing HOV lane priority dynamic control by vehicle mileage saving rate and reduction rate of per capita travel time consumption. The flow chart is shown in Figure6.Figure 6
The evaluation process of implementing HOV lane priority dynamic control.


### 2.5.1. Traffic Information Acquisition in Mixed Traffic

Assume there arem sections in the road network and n cars in each section, then the vehicle mileage of the road network in the most initial operating state (mixed traffic) can be expressed as follows:(7)S0=∑j=0m∑i=0nSij0,where Sij0 is the mileage of the ith vehicle in the jth section of the road network and S0 is the total mileage of the vehicles.Then, the total travel time in the initial operating state could be calculated as follows:(8)PI0=Pa0∗Ta0+Pb0∗Tb0+Pc0∗Tc0,where PI0 is the total travel time, Pa0 is the number of noncarpooling travelers, Ta0 is the average travel time of noncarpooling travelers, Pb0 is the number of carpooling travelers, Tb0 is the average travel time of carpooling travelers,Pc0 is the number of public transportation travelers, and Ta0 is the average travel time of public transportation travelers.


### 2.5.2. Transportation Mode Transfer

After the implementation of the HOV lane priority dynamic control, the trips of low-occupancy vehicles (private cars) in the road network will shift to high-occupancy vehicles (carpool). Through presurvey, the travel mode transfer function under different states is obtained, as shown in Table3.Table 3
The state functions of the transfer from private car to carpool.
StatePercentage increase in travel time (k)Transfer functionf(k)1<10%f(k) = −3.84k + 0.6293210%–30%f(k) = −1.179k + 0.3765330%–40%f(k) = −0.9735k + 0.4224440%–50%f(k) = −0.6045k + 0.08255>50%f(k) = −0.7168k + 0.0029


### 2.5.3. Traffic Information Acquisition in Traffic with HOV Lanes

Assume there arem sections in the road network and n cars in each section, and then, the total vehicle mileage of the road network in the posterior operating state (after setting HOV lanes) can be expressed as follows:(9)S1=∑j=0m∑i=0nSij1,where Sij1 is the mileage of the i-th vehicle in the j-th section of the road network and S1 is the total mileage of the vehicles.Then, the total travel time in the v could be calculated as follows:(10)PI1=Pa1∗Ta1+Pb1∗Tb1+Pc1∗Tc1,where PI1 is the total travel time, Pa1 is the number of noncarpooling travelers, Ta1 is the average travel time of noncarpooling travelers, Pb1 is the number of carpooling travelers, Tb1 is the average travel time of carpooling travelers,Pc1 is the number of public transportation travelers, and Ta1 is the average travel time of public transportation travelers.


### 2.5.4. Operating Efficiency Evaluation

The percentage reduction in total travel mileage can be expressed as follows:(11)M=∑j=0m∑i=0nSij0−∑j=0m∑i=0nSij1∑j=0m∑i=0nSij0.Similarly, the percentage reduction in per capita travel time can be expressed as follows:(12)p=PI0/Pao+Pbo+Pco−PI/Pa1+Pb1+Pc1PI0/Pao+Pbo+Pco.


### 2.5.5. Energy Consumption Evaluation

Evaluation and comparison of road network energy consumption before and after HOV lane priority dynamic control is of great significance for the promotion and application of HOV lanes. According to the literature [22, 23], the energy consumption of different transportation modes in cities is summarized in Tables 4 and 5.Table 4
Energy consumption comparison of different types of vehicles.
Vehicle categoriesSedanPublic busTaxiPrivate carBus with multiple compartmentsBus with single compartmentFuel consumption (liter/100 km)10.21125.522.5Energy consumption (liter/(100 people∗km))7.346.780.410.73Energy consumption (kg standard coal/(100 people∗km)）8.527.870.480.85Note: coefficient for standard coal to fuel conversion = 0.7895 kg/liter × 1.4714 kg standard coal/kg = 1.1617 kg standard coal/liter.Table 5
Energy consumption comparison of different types of vehicles with different occupancies.
Vehicle categoriesSeating capacitiesEnergy consumption under different occupancies (liter/100 people∗km)25%50%75%100%SedanTaxi47.1593.7592.682.066Private car510.175.093.762.95Public busBus with multiple compartments801.280.700.510.41Bus with single compartment402.251.240.900.73According to the actual situation of the investigated city, the energy consumption of noncarpooling private car trips, carpooling private car trips, and public bus trips with single compartment was selected as 10.17 (25%), 3.67 (75%), and 1.24 (50%), respectively.The total energy-saving rate of road network can be calculated by the following equation:(13)H=αm·Pa0·Ja0·Qa0+βn·Pb0·Jb0·Qb0+γg·Pc0·Jc0·Qc0−αm·Pa1·Ja1·Qa1+βn·Pb1·Jb1·Qb1+γg·Pc1·Jc1·Qc1αm·Pa0·Ja0·Qa0+βn·Pb0·Jb0·Qb0+γg·Pc0·Jc0·Qc0,where H is the total energy-saving rate of road network;  αm is the energy consumption coefficient of noncarpooling trips, 10.17 × 10−5 L/p·m;  βn is the energy consumption coefficient of carpooling trips, 3.76 × 10−5 L/p·m;  γg is the energy consumption coefficient of public bus trips, 1.24 × 10−5 L/p·m; Ja0 is the average travel mileage of noncarpooling trips in the initial operating state (mixed traffic), m;  Jb0 is the average travel mileage of carpooling trips in the initial operating state (mixed traffic), m; Jc0 is the average travel mileage of public bus trips in the initial operating state (mixed traffic), m;  Qa0 is the number of vehicles of noncarpooling trips in the initial operating state (mixed traffic), veh;  Qb0 is the number of vehicles of carpooling trips in the initial operating state (mixed traffic), veh; Qc0 is the number of vehicles of public bus trips in the initial operating state (mixed traffic), veh; Ja1 is the average travel mileage of noncarpooling trips in the posterior operating state (after setting HOV lanes), m; Jb1 is the average travel mileage of carpooling trips in the posterior operating state (after setting HOV lanes), m; Jc1 is the average travel mileage of bus trips in the posterior operating state (after setting HOV lanes), m;  Qa1 is the number of vehicles of noncarpooling trips in the posterior operating state (after setting HOV lanes), veh;  Qb1 is the number of vehicles of carpooling trips in the posterior operating state (after setting HOV lanes), veh; and Qc1 is the number of vehicles of public bus trips in the posterior operating state (after setting HOV lanes), veh.


## 2.5.1. Traffic Information Acquisition in Mixed Traffic

Assume there arem sections in the road network and n cars in each section, then the vehicle mileage of the road network in the most initial operating state (mixed traffic) can be expressed as follows:(7)S0=∑j=0m∑i=0nSij0,where Sij0 is the mileage of the ith vehicle in the jth section of the road network and S0 is the total mileage of the vehicles.Then, the total travel time in the initial operating state could be calculated as follows:(8)PI0=Pa0∗Ta0+Pb0∗Tb0+Pc0∗Tc0,where PI0 is the total travel time, Pa0 is the number of noncarpooling travelers, Ta0 is the average travel time of noncarpooling travelers, Pb0 is the number of carpooling travelers, Tb0 is the average travel time of carpooling travelers,Pc0 is the number of public transportation travelers, and Ta0 is the average travel time of public transportation travelers.


## 2.5.2. Transportation Mode Transfer

After the implementation of the HOV lane priority dynamic control, the trips of low-occupancy vehicles (private cars) in the road network will shift to high-occupancy vehicles (carpool). Through presurvey, the travel mode transfer function under different states is obtained, as shown in Table3.Table 3
The state functions of the transfer from private car to carpool.
StatePercentage increase in travel time (k)Transfer functionf(k)1<10%f(k) = −3.84k + 0.6293210%–30%f(k) = −1.179k + 0.3765330%–40%f(k) = −0.9735k + 0.4224440%–50%f(k) = −0.6045k + 0.08255>50%f(k) = −0.7168k + 0.0029


## 2.5.3. Traffic Information Acquisition in Traffic with HOV Lanes

Assume there arem sections in the road network and n cars in each section, and then, the total vehicle mileage of the road network in the posterior operating state (after setting HOV lanes) can be expressed as follows:(9)S1=∑j=0m∑i=0nSij1,where Sij1 is the mileage of the i-th vehicle in the j-th section of the road network and S1 is the total mileage of the vehicles.Then, the total travel time in the v could be calculated as follows:(10)PI1=Pa1∗Ta1+Pb1∗Tb1+Pc1∗Tc1,where PI1 is the total travel time, Pa1 is the number of noncarpooling travelers, Ta1 is the average travel time of noncarpooling travelers, Pb1 is the number of carpooling travelers, Tb1 is the average travel time of carpooling travelers,Pc1 is the number of public transportation travelers, and Ta1 is the average travel time of public transportation travelers.


## 2.5.4. Operating Efficiency Evaluation

The percentage reduction in total travel mileage can be expressed as follows:(11)M=∑j=0m∑i=0nSij0−∑j=0m∑i=0nSij1∑j=0m∑i=0nSij0.Similarly, the percentage reduction in per capita travel time can be expressed as follows:(12)p=PI0/Pao+Pbo+Pco−PI/Pa1+Pb1+Pc1PI0/Pao+Pbo+Pco.


## 2.5.5. Energy Consumption Evaluation

Evaluation and comparison of road network energy consumption before and after HOV lane priority dynamic control is of great significance for the promotion and application of HOV lanes. According to the literature [22, 23], the energy consumption of different transportation modes in cities is summarized in Tables 4 and 5.Table 4
Energy consumption comparison of different types of vehicles.
Vehicle categoriesSedanPublic busTaxiPrivate carBus with multiple compartmentsBus with single compartmentFuel consumption (liter/100 km)10.21125.522.5Energy consumption (liter/(100 people∗km))7.346.780.410.73Energy consumption (kg standard coal/(100 people∗km)）8.527.870.480.85Note: coefficient for standard coal to fuel conversion = 0.7895 kg/liter × 1.4714 kg standard coal/kg = 1.1617 kg standard coal/liter.Table 5
Energy consumption comparison of different types of vehicles with different occupancies.
Vehicle categoriesSeating capacitiesEnergy consumption under different occupancies (liter/100 people∗km)25%50%75%100%SedanTaxi47.1593.7592.682.066Private car510.175.093.762.95Public busBus with multiple compartments801.280.700.510.41Bus with single compartment402.251.240.900.73According to the actual situation of the investigated city, the energy consumption of noncarpooling private car trips, carpooling private car trips, and public bus trips with single compartment was selected as 10.17 (25%), 3.67 (75%), and 1.24 (50%), respectively.The total energy-saving rate of road network can be calculated by the following equation:(13)H=αm·Pa0·Ja0·Qa0+βn·Pb0·Jb0·Qb0+γg·Pc0·Jc0·Qc0−αm·Pa1·Ja1·Qa1+βn·Pb1·Jb1·Qb1+γg·Pc1·Jc1·Qc1αm·Pa0·Ja0·Qa0+βn·Pb0·Jb0·Qb0+γg·Pc0·Jc0·Qc0,where H is the total energy-saving rate of road network;  αm is the energy consumption coefficient of noncarpooling trips, 10.17 × 10−5 L/p·m;  βn is the energy consumption coefficient of carpooling trips, 3.76 × 10−5 L/p·m;  γg is the energy consumption coefficient of public bus trips, 1.24 × 10−5 L/p·m; Ja0 is the average travel mileage of noncarpooling trips in the initial operating state (mixed traffic), m;  Jb0 is the average travel mileage of carpooling trips in the initial operating state (mixed traffic), m; Jc0 is the average travel mileage of public bus trips in the initial operating state (mixed traffic), m;  Qa0 is the number of vehicles of noncarpooling trips in the initial operating state (mixed traffic), veh;  Qb0 is the number of vehicles of carpooling trips in the initial operating state (mixed traffic), veh; Qc0 is the number of vehicles of public bus trips in the initial operating state (mixed traffic), veh; Ja1 is the average travel mileage of noncarpooling trips in the posterior operating state (after setting HOV lanes), m; Jb1 is the average travel mileage of carpooling trips in the posterior operating state (after setting HOV lanes), m; Jc1 is the average travel mileage of bus trips in the posterior operating state (after setting HOV lanes), m;  Qa1 is the number of vehicles of noncarpooling trips in the posterior operating state (after setting HOV lanes), veh;  Qb1 is the number of vehicles of carpooling trips in the posterior operating state (after setting HOV lanes), veh; and Qc1 is the number of vehicles of public bus trips in the posterior operating state (after setting HOV lanes), veh.


## 3. Case Study-HOV Lane Dynamic Control in Wuxi City, China

### 3.1. HOV Lane Dynamic Control Scheme in Wuxi City

Wuxi, Jiangsu, is the first city in China to implement HOV lane priority dynamic management and has achieved good results. Both Liangxi District and Xinwu District of Wuxi City are located in the southeast of Jiangsu Province and are located in the city center of Wuxi. The current resident population of Liangxi District is 950,000, and the current resident population of Xinwu District is 364,400. On May 16, 2014, China's first dedicated carpooling lane “HOV lane” was introduced in Wuxi City.In field survey, the following roads shown in Table6 were selected to investigate the threshold of setting HOV lanes.Table 6
Traffic information of the selected roads.
Traffic directionRoad codeRoad nameOne-wayNo. of lanesPeak hour traffic volume (pcu/h)Length (m)Northbound/Southbound1Changjiang North RoadNo6154841202Xingyuan Middle RoadNo6194243603Tangnan RoadNo6192037304Tongyang Road (extended to Jiefang North Road)No411524920Eastbound/Westbound5Tongjiang RoadNo8173627106Renmin East RoadNo6298423307Xueqian East RoadNo6227523408Yongle East RoadNo6169736909South Ring RoadNo679343470According to the survey, carpooling trips account for 5% of the total private car trips in Wuxi City. Firstly, equation (3) was used to calculate the traffic speed of each road and determine the average delay time considering the signal control of the intersection to obtain the operating efficiency of private car trips in the area, as shown in Table 7.Table 7
Operation efficiency of the road network in the investigated area.
Road codeRoad nameTraffic volume per hour (pcu/h)Length (m)Free-flow speed (km/h)Traffic speed (km/h)1Changjiang North Road1548412060542Xingyuan Middle Road1942436060563Tangnan Road1920373050454Tongyang Road (extended to Jiefang North Road)1152492040325Tongjiang Road1736271080756Renmin East Road2984233040357Xueqian East Road2275234040328Yongle East Road1697369040369South Ring Road79343470807110East Ring Road104516200807311Xingchang South Road322144508067The operation efficiency of the intersections in the investigated area is summarized in Table8, and the travel time and travel mileage of different travel modes in the initial operating state are summarized in Table 9.Table 8
Operation efficiency of the intersections.
Intersection codeName of the intersecting roadsTraffic volume (pcu/h)Signal cycle (s)Per capita delay (s)1Tongyang Road, Tongjiang Road, and Xingyuan Middle Road5618025.362Xingyuan Middle Road and Renmin East Road148412530.913Tongyang Road and Renmin East Road4646022.154Tangnan Road and Renmin East Road1434No signal—5Xingyuan Middle Road and Renmin East Road4738030.156Tongyang Road and Xueqian East Road3976018.367Tangnan Road and Xueqian East Road15698042.368Xingyuan Middle Road and Xueqian East Road5128035.129Changjiang North Road and Xueqian East Road83312040.4810Tongyang Road and Yongle East Road4835518.2311Tangnan Road and Yongle East Road182911037.5212Xingyuan Middle Road and Yongle East Road16697524.5813Changjiang North Road and Yongle East Road94812027.9314Tongyang Road and South Ring Road617No signal—15Tangnan Road and South Ring Road1973No signal—16Xingyuan Middle Road and South Ring Road1967No signal—17Changjiang North Road and South Ring Road1132No signal—Table 9
Travel time and travel mileage of different travel modes in the initial operating state (mixed traffic).
CodeTravel modeInitial operating state (mixed traffic)Number of vehicles (veh)Number of travelers (p)Travel time (s)Travel mileage (m)1Noncarpooling private car trips2318823188105432432Carpooling private car trips3841360162549703Public bus trips816679613264409Sum—2438831344——Travelers in Wuxi City can make reservations online according to their travel time and route in advance. The online system will automatically match according to user needs and supply. This section will scientifically evaluate the efficiency of Wuxi carpooling trips.Carpooling travel time is mainly composed of waiting time, travel time, and detour time. The travel time is determined by the travel path. The waiting time and detour time are mainly determined by the time and space distribution density of carpooling travelers, as shown in Table10.Table 10
Travel time and detour time for different proportions of carpool trips.
Proportion of carpooling trips (%)Area (km2)No. of vehicles (veh)Time density (veh/s)Coverage (m)Waiting time (s)Detour time (s)Total (s)514.874068.86267.7829865895510.014.878134.43189.3521035956915.014.8712192.95154.6017225943120.014.8716262.21133.8914920935825.014.8720321.77119.7513318031330.014.8724391.48109.3212116028135.014.8728451.27101.2111214525840.014.8732521.1194.6710513524045.014.8736580.9889.269912622650.014.8740650.8984.6894120214


### 3.2. Efficiency and Energy Consumption Evaluation of HOV Lane Priority Dynamic Control in Wuxi City

#### 3.2.1. Preliminary Analysis of Operation Efficiency

After setting up HOV lane, the traffic speed of private cars on ordinary lanes (noncarpooling lanes) is shown in Table11.Table 11
The traffic speed of private cars on ordinary lanes.
CodeRoad nameTraffic volume per hour (pcu/h)Length (m)Free-flow speed (km/h)1Changjiang North Road412060402Xingyuan Middle Road436060443Tangnan Road373050344Tongyang Road (extended to Jiefang North Road)492040285Tongjiang Road271080486Renmin East Road233040277Xueqian East Road234040228Yongle East Road369040189South Ring Road3470804210East Ring Road6200803611Xingchang South Road44508045After setting up HOV lane, the traffic speed of private cars on the carpooling lanes is shown in Table12.Table 12
The speed of private cars on HOV lanes.
CodeRoad nameTraffic volume per hour (pcu/h)Length (m)Free-flow speed (km/h)1Changjiang North Road412060602Xingyuan Middle Road436060563Tangnan Road373050504Tongyang Road (extended to Jiefang North Road)492040385Tongjiang Road271080786Renmin East Road233040357Xueqian East Road234040328Yongle East Road369040409South Ring Road3470807110East Ring Road6200807511Xingchang South Road44508074The travel time of noncarpooling private car trips and carpooling private car trips is calculated and summarized in Table13.Table 13
Travel time and travel mileage of different travel modes in posterior operating state (with HOV lanes).
CodeTravel modesPosterior operating state (with HOV lanes)Number of vehicles (veh)Number of travelers (p)Travel time (s)Travel mileage (m)1Noncarpooling private car trips2318823188106032432Carpooling private car trips3841360129149703Public bus trips816679612874409Sum—2438831344——


#### 3.2.2. Travel Mode Transfer

Based on of the influence of the increment of travel time on carpooling behavior, after setting HOV lanes, the increase in carpooling travel time is 21.7% compared with that of noncarpooling travel time. The transfer ratio of low-occupancy travel mode to high-occupancy travel mode is 12.0%.


#### 3.2.3. Operation Efficiency Analysis after Travel Mode Transferring

The travel time and travel mileage of different travel modes after travel mode transferring are summarized in Table14. Moreover, the comparison of number of trips, number of travelers, travel time, and travel mileage in initial (mixed traffic) and posterior operating state (after travel mode transferring) is presented in Figures 7–10, respectively.Table 14
Travel time and travel mileage of different travel modes after travel mode transferring in the posterior operating state (with HOV lanes).
CodeTravel modePosterior operating state (with HOV lanes)Number of vehicles (veh)Number of travelers (p)Travel time (s)Travel mileage (m)1Noncarpooling private car trips2040520405100632432Carpooling private car trips15684143122544383Public bus trips816679612564409Sum—2278931344——Figure 7
Comparison of number of trips before and after implementing HOV lanes priority dynamic control for different travel modes.Figure 8
Comparison of number of travelers before and after implementing HOV lanes priority dynamic control for different travel modes.Figure 9
Comparison of travel time before and after implementing HOV lanes priority dynamic control for different travel modes.Figure 10
Comparison of travel mileage before and after implementing HOV lanes priority dynamic control for different travel modes.


#### 3.2.4. Final Evaluation of Operation Efficiency and Energy Consumption

The percentage reduction in total travel mileage can be calculated as follows:(14)M=80704908−7672994380704908=4.93%.The percentage reduction in per capita travel time can be calculated as follows:(15)p=1138−10891138=4.27%.The total energy-saving rate of the road network can be calculated as follows:(16)H=177735785.9−138709510.2177735785.9=21.96%.To sum up, after HOV lane priority dynamic control was implemented and travel mode transferring was completed, the total mileage of vehicles on the road network was saved by 4.93% and the per capita travel time decreased from 1138 s to 1089 s, with a reduction rate of 4.27%; the total energy consumption of trips in the network was reduced by 39,26275.62 L, with a saving rate of 21.96%.


## 3.1. HOV Lane Dynamic Control Scheme in Wuxi City

Wuxi, Jiangsu, is the first city in China to implement HOV lane priority dynamic management and has achieved good results. Both Liangxi District and Xinwu District of Wuxi City are located in the southeast of Jiangsu Province and are located in the city center of Wuxi. The current resident population of Liangxi District is 950,000, and the current resident population of Xinwu District is 364,400. On May 16, 2014, China's first dedicated carpooling lane “HOV lane” was introduced in Wuxi City.In field survey, the following roads shown in Table6 were selected to investigate the threshold of setting HOV lanes.Table 6
Traffic information of the selected roads.
Traffic directionRoad codeRoad nameOne-wayNo. of lanesPeak hour traffic volume (pcu/h)Length (m)Northbound/Southbound1Changjiang North RoadNo6154841202Xingyuan Middle RoadNo6194243603Tangnan RoadNo6192037304Tongyang Road (extended to Jiefang North Road)No411524920Eastbound/Westbound5Tongjiang RoadNo8173627106Renmin East RoadNo6298423307Xueqian East RoadNo6227523408Yongle East RoadNo6169736909South Ring RoadNo679343470According to the survey, carpooling trips account for 5% of the total private car trips in Wuxi City. Firstly, equation (3) was used to calculate the traffic speed of each road and determine the average delay time considering the signal control of the intersection to obtain the operating efficiency of private car trips in the area, as shown in Table 7.Table 7
Operation efficiency of the road network in the investigated area.
Road codeRoad nameTraffic volume per hour (pcu/h)Length (m)Free-flow speed (km/h)Traffic speed (km/h)1Changjiang North Road1548412060542Xingyuan Middle Road1942436060563Tangnan Road1920373050454Tongyang Road (extended to Jiefang North Road)1152492040325Tongjiang Road1736271080756Renmin East Road2984233040357Xueqian East Road2275234040328Yongle East Road1697369040369South Ring Road79343470807110East Ring Road104516200807311Xingchang South Road322144508067The operation efficiency of the intersections in the investigated area is summarized in Table8, and the travel time and travel mileage of different travel modes in the initial operating state are summarized in Table 9.Table 8
Operation efficiency of the intersections.
Intersection codeName of the intersecting roadsTraffic volume (pcu/h)Signal cycle (s)Per capita delay (s)1Tongyang Road, Tongjiang Road, and Xingyuan Middle Road5618025.362Xingyuan Middle Road and Renmin East Road148412530.913Tongyang Road and Renmin East Road4646022.154Tangnan Road and Renmin East Road1434No signal—5Xingyuan Middle Road and Renmin East Road4738030.156Tongyang Road and Xueqian East Road3976018.367Tangnan Road and Xueqian East Road15698042.368Xingyuan Middle Road and Xueqian East Road5128035.129Changjiang North Road and Xueqian East Road83312040.4810Tongyang Road and Yongle East Road4835518.2311Tangnan Road and Yongle East Road182911037.5212Xingyuan Middle Road and Yongle East Road16697524.5813Changjiang North Road and Yongle East Road94812027.9314Tongyang Road and South Ring Road617No signal—15Tangnan Road and South Ring Road1973No signal—16Xingyuan Middle Road and South Ring Road1967No signal—17Changjiang North Road and South Ring Road1132No signal—Table 9
Travel time and travel mileage of different travel modes in the initial operating state (mixed traffic).
CodeTravel modeInitial operating state (mixed traffic)Number of vehicles (veh)Number of travelers (p)Travel time (s)Travel mileage (m)1Noncarpooling private car trips2318823188105432432Carpooling private car trips3841360162549703Public bus trips816679613264409Sum—2438831344——Travelers in Wuxi City can make reservations online according to their travel time and route in advance. The online system will automatically match according to user needs and supply. This section will scientifically evaluate the efficiency of Wuxi carpooling trips.Carpooling travel time is mainly composed of waiting time, travel time, and detour time. The travel time is determined by the travel path. The waiting time and detour time are mainly determined by the time and space distribution density of carpooling travelers, as shown in Table10.Table 10
Travel time and detour time for different proportions of carpool trips.
Proportion of carpooling trips (%)Area (km2)No. of vehicles (veh)Time density (veh/s)Coverage (m)Waiting time (s)Detour time (s)Total (s)514.874068.86267.7829865895510.014.878134.43189.3521035956915.014.8712192.95154.6017225943120.014.8716262.21133.8914920935825.014.8720321.77119.7513318031330.014.8724391.48109.3212116028135.014.8728451.27101.2111214525840.014.8732521.1194.6710513524045.014.8736580.9889.269912622650.014.8740650.8984.6894120214


## 3.2. Efficiency and Energy Consumption Evaluation of HOV Lane Priority Dynamic Control in Wuxi City

### 3.2.1. Preliminary Analysis of Operation Efficiency

After setting up HOV lane, the traffic speed of private cars on ordinary lanes (noncarpooling lanes) is shown in Table11.Table 11
The traffic speed of private cars on ordinary lanes.
CodeRoad nameTraffic volume per hour (pcu/h)Length (m)Free-flow speed (km/h)1Changjiang North Road412060402Xingyuan Middle Road436060443Tangnan Road373050344Tongyang Road (extended to Jiefang North Road)492040285Tongjiang Road271080486Renmin East Road233040277Xueqian East Road234040228Yongle East Road369040189South Ring Road3470804210East Ring Road6200803611Xingchang South Road44508045After setting up HOV lane, the traffic speed of private cars on the carpooling lanes is shown in Table12.Table 12
The speed of private cars on HOV lanes.
CodeRoad nameTraffic volume per hour (pcu/h)Length (m)Free-flow speed (km/h)1Changjiang North Road412060602Xingyuan Middle Road436060563Tangnan Road373050504Tongyang Road (extended to Jiefang North Road)492040385Tongjiang Road271080786Renmin East Road233040357Xueqian East Road234040328Yongle East Road369040409South Ring Road3470807110East Ring Road6200807511Xingchang South Road44508074The travel time of noncarpooling private car trips and carpooling private car trips is calculated and summarized in Table13.Table 13
Travel time and travel mileage of different travel modes in posterior operating state (with HOV lanes).
CodeTravel modesPosterior operating state (with HOV lanes)Number of vehicles (veh)Number of travelers (p)Travel time (s)Travel mileage (m)1Noncarpooling private car trips2318823188106032432Carpooling private car trips3841360129149703Public bus trips816679612874409Sum—2438831344——


### 3.2.2. Travel Mode Transfer

Based on of the influence of the increment of travel time on carpooling behavior, after setting HOV lanes, the increase in carpooling travel time is 21.7% compared with that of noncarpooling travel time. The transfer ratio of low-occupancy travel mode to high-occupancy travel mode is 12.0%.


### 3.2.3. Operation Efficiency Analysis after Travel Mode Transferring

The travel time and travel mileage of different travel modes after travel mode transferring are summarized in Table14. Moreover, the comparison of number of trips, number of travelers, travel time, and travel mileage in initial (mixed traffic) and posterior operating state (after travel mode transferring) is presented in Figures 7–10, respectively.Table 14
Travel time and travel mileage of different travel modes after travel mode transferring in the posterior operating state (with HOV lanes).
CodeTravel modePosterior operating state (with HOV lanes)Number of vehicles (veh)Number of travelers (p)Travel time (s)Travel mileage (m)1Noncarpooling private car trips2040520405100632432Carpooling private car trips15684143122544383Public bus trips816679612564409Sum—2278931344——Figure 7
Comparison of number of trips before and after implementing HOV lanes priority dynamic control for different travel modes.Figure 8
Comparison of number of travelers before and after implementing HOV lanes priority dynamic control for different travel modes.Figure 9
Comparison of travel time before and after implementing HOV lanes priority dynamic control for different travel modes.Figure 10
Comparison of travel mileage before and after implementing HOV lanes priority dynamic control for different travel modes.


### 3.2.4. Final Evaluation of Operation Efficiency and Energy Consumption

The percentage reduction in total travel mileage can be calculated as follows:(14)M=80704908−7672994380704908=4.93%.The percentage reduction in per capita travel time can be calculated as follows:(15)p=1138−10891138=4.27%.The total energy-saving rate of the road network can be calculated as follows:(16)H=177735785.9−138709510.2177735785.9=21.96%.To sum up, after HOV lane priority dynamic control was implemented and travel mode transferring was completed, the total mileage of vehicles on the road network was saved by 4.93% and the per capita travel time decreased from 1138 s to 1089 s, with a reduction rate of 4.27%; the total energy consumption of trips in the network was reduced by 39,26275.62 L, with a saving rate of 21.96%.


## 3.2.1. Preliminary Analysis of Operation Efficiency

After setting up HOV lane, the traffic speed of private cars on ordinary lanes (noncarpooling lanes) is shown in Table11.Table 11
The traffic speed of private cars on ordinary lanes.
CodeRoad nameTraffic volume per hour (pcu/h)Length (m)Free-flow speed (km/h)1Changjiang North Road412060402Xingyuan Middle Road436060443Tangnan Road373050344Tongyang Road (extended to Jiefang North Road)492040285Tongjiang Road271080486Renmin East Road233040277Xueqian East Road234040228Yongle East Road369040189South Ring Road3470804210East Ring Road6200803611Xingchang South Road44508045After setting up HOV lane, the traffic speed of private cars on the carpooling lanes is shown in Table12.Table 12
The speed of private cars on HOV lanes.
CodeRoad nameTraffic volume per hour (pcu/h)Length (m)Free-flow speed (km/h)1Changjiang North Road412060602Xingyuan Middle Road436060563Tangnan Road373050504Tongyang Road (extended to Jiefang North Road)492040385Tongjiang Road271080786Renmin East Road233040357Xueqian East Road234040328Yongle East Road369040409South Ring Road3470807110East Ring Road6200807511Xingchang South Road44508074The travel time of noncarpooling private car trips and carpooling private car trips is calculated and summarized in Table13.Table 13
Travel time and travel mileage of different travel modes in posterior operating state (with HOV lanes).
CodeTravel modesPosterior operating state (with HOV lanes)Number of vehicles (veh)Number of travelers (p)Travel time (s)Travel mileage (m)1Noncarpooling private car trips2318823188106032432Carpooling private car trips3841360129149703Public bus trips816679612874409Sum—2438831344——


## 3.2.2. Travel Mode Transfer

Based on of the influence of the increment of travel time on carpooling behavior, after setting HOV lanes, the increase in carpooling travel time is 21.7% compared with that of noncarpooling travel time. The transfer ratio of low-occupancy travel mode to high-occupancy travel mode is 12.0%.


## 3.2.3. Operation Efficiency Analysis after Travel Mode Transferring

The travel time and travel mileage of different travel modes after travel mode transferring are summarized in Table14. Moreover, the comparison of number of trips, number of travelers, travel time, and travel mileage in initial (mixed traffic) and posterior operating state (after travel mode transferring) is presented in Figures 7–10, respectively.Table 14
Travel time and travel mileage of different travel modes after travel mode transferring in the posterior operating state (with HOV lanes).
CodeTravel modePosterior operating state (with HOV lanes)Number of vehicles (veh)Number of travelers (p)Travel time (s)Travel mileage (m)1Noncarpooling private car trips2040520405100632432Carpooling private car trips15684143122544383Public bus trips816679612564409Sum—2278931344——Figure 7
Comparison of number of trips before and after implementing HOV lanes priority dynamic control for different travel modes.Figure 8
Comparison of number of travelers before and after implementing HOV lanes priority dynamic control for different travel modes.Figure 9
Comparison of travel time before and after implementing HOV lanes priority dynamic control for different travel modes.Figure 10
Comparison of travel mileage before and after implementing HOV lanes priority dynamic control for different travel modes.


## 3.2.4. Final Evaluation of Operation Efficiency and Energy Consumption

The percentage reduction in total travel mileage can be calculated as follows:(14)M=80704908−7672994380704908=4.93%.The percentage reduction in per capita travel time can be calculated as follows:(15)p=1138−10891138=4.27%.The total energy-saving rate of the road network can be calculated as follows:(16)H=177735785.9−138709510.2177735785.9=21.96%.To sum up, after HOV lane priority dynamic control was implemented and travel mode transferring was completed, the total mileage of vehicles on the road network was saved by 4.93% and the per capita travel time decreased from 1138 s to 1089 s, with a reduction rate of 4.27%; the total energy consumption of trips in the network was reduced by 39,26275.62 L, with a saving rate of 21.96%.


## 4. Conclusions

This paper first summarized the current research on HOV lane implementation and analyzed and identifies the threshold of setting road HOV lane dynamic control under the connected vehicle environment. Moreover, the HOV lane priority dynamic control process was determined, and the operating efficiency and energy consumption evaluation method was proposed. A case study in Wuxi City, China, was carried out. The results showed that, after implementing the HOV lane priority dynamic control, the total mileage of road network vehicles was saved by 4.93%, the average travel time per capita was reduced by 4.27%, and the total energy-saving rate of road network travel was 21.96%. From the results, it can be seen that dynamic control of HOV lanes with priority for carpooling can save the total mileage of vehicles in the road network, the average travel time per capita, and the total energy consumption, thus improving travel efficiency. With the further development of IoV technology, the dynamic management and control of HOV lanes can be combined with real-time dynamic reversible lane technology to achieve real-time dynamic control of HOV reversible lanes to achieve precise control optimization.



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*Source: 8892859-2020-08-08.xml*