Optimization Models of Actuated Control Considering Vehicle Queuing for Sustainable Operation

Round 1

Reviewer 1 Report

The authors proposed the title: Optimization Models of Actuated Control Considering Vehicle Queuing for Sustainable Operation.

The following comments should be included in the manuscript

1. I am seeing the references in the manuscript as old years, latest references should be incorporated in the manuscript.

2. Novelty should be appropriately described in the manuscript.

3. Why use only 30-periodic simulations?

4. Comparative analysis of existing work with novel work should be there.

5. Can be modified the objective function and constraints of phase schemes?

6. Why use the different format in the first line of the second para of the introduction section?

 

Author Response

1. I am seeing the references in the manuscript as old years, latest references should be incorporated in the manuscript.

Thank you very much for your suggestion, we have added the latest references according to it.

2. Novelty should be appropriately described in the manuscript.

Thank you very much for your suggestion. We have added the research novelty in the Conclusion sections which is now specifically written as ‘It can be seen that compared with previous studies, this paper focuses on the in-fluence of queued vehicles, and two basic control parameters, the minimum green time and the maximum green time, are optimized to achieve better control effect. Through this study, more reasonable control parameters can be obtained, so as to avoid green loss, reduce vehicle delay and improve traffic operation sustainability.’

3. Why use only 30-periodic simulations?

In this paper, VISSIM is used to simulate and verify the minimum green time calculation model. The maximum simulation time of VISSIM is 3600s, and the cycle required for one simulation is 55s. In order to form a stable queue in the simulation, this paper takes the second half of the VISSIM maximum simulation cycle (3600s), the data of the last 1800s, which is about 30-period simulations.

4. Comparative analysis of existing work with novel work should be there.

Thank you very much for your suggestion. We have added the comparative analysis in the Literature Review section, which is now specifically written as ‘Above all, we can found that that: a) The optimization models constructed in re-cent years mostly rely on the real-time data obtained by intelligent detectors, but these data are not easy to obtain in most intersections at present, and the accuracy and reli-ability of the data still need to be further studied. Therefore, these models lack certain applicability. b) There is less research on the minimum green time, and these research-es mainly focus on the arrival characteristics of vehicles, ignoring the impact of queued vehicles. c) Researches on the maximum green time mainly focus on the traffic flow characteristics, ignoring in-depth discussion of phase schemes and queued vehicles. To deal with the abovementioned issues, this paper has done the following work: a) This paper first establishes an improved traffic wave model, and then proposes a vehi-cle queuing model based on it. Then, a minimum green time calculation model consid-ering queued vehicles is proposed, which takes fully consideration of the impact of the queued vehicles to the control effect. b) A maximum green time calculation model considering phase schemes and queued vehicles is established, which deeply discuss the phase schemes and queued vehicles impacts. c) The data needed in this paper can be accurately obtained at almost intersections through coil detectors, which means that the models constructed in this paper has stronger practical value.’

5. Can be modified the objective function and constraints of phase schemes?

Thank you very much for your suggestion. This paper mainly considers the optimization of control parameters, that is, the minimum green time and the maximum green time considering queued vehicles. We believe that these two basic parameters can be calculated by using the objective function and constraints proposed in this paper under different phase schemes. The actual green time under different phase schemes needs to be specifically determined according to the minimum green time and the extensive green time, and is constrained by the maximum green time. For your suggestion on different phase schemes, we plan to discussed this issue in subsequent research. We expect to propose phase switch parameters which can decide to when to switch the phase or change phase schemes, supporting decision-making in various cases.

 

6. Why use the different format in the first line of the second para of the introduction section?

Outline for building a powerful transportation country is a major policy issued by China in 2020, so this sentence is in italics, mainly to reflect its importance. Thank you for your suggestion. Now it has been revised, and the emphasis has been removed.

Author Response File: Author Response.pdf

Reviewer 2 Report

This manuscript discussed the vehicle queuing modeling at actuated intersections, its influence on signal timing as well. The accuracy and optimization effect of the proposed models are verified by simulation. The topic is hot and fits the scope of the journal. The research work and results may benefit the sustainability improvement of intersection traffic.

Some specific comments on the content are listed below for future revision work.

1.       In Section 1, the third paragraph, the author said “the intelligence and automation level of most intersections cannot meet the requirements”, how do we understand this conclusion about intelligence? Does it contradict with the conclusion of this manuscript?

2.       As an international journal, the author does not need to emphasize which one is domestic, which one is overseas, they all international scholars working in this field.

3.       In Section 1, the author said two main contents of this manuscript are minimum green time calculation modeling and maximum green time calculation modeling, why? Why does the author have to discuss these two parameters? What are the difference between them? The research necessity should be clear in Introduction part, which can help the reviewer understand the target and contribution of this manuscript.

4.       In Section 3, the content and variables definition in the third paragraph is inconsistent with the marks and contents of Fig.1b.

5.       What does y_i mean in equation 16?

6.       Passive voice is generally used in technical papers. Thus, the voice of some sentences needs to be modified, such as the sentence above the Eq.17.

7.       In section 4, the author established an optimization model for the maximum green time according to the NEMA phase structure, but the reason and applicability does not have any discussion. Moreover, as the most research work in this manuscript, besides application this existing phase schemes, what is the main contribution of this manuscript, it should be highlighted throughout the paper.

8.       In section 4, according to the equation 15, as for the second objective, whether the traffic flow capacity in other directions perpendicular to this traffic flow should also be included in the objective function in overall traffic system view?

9.       What does the variables mean in the first column of Table 5?

10.    Why do the optimization ratio results shown in Table 7 have big difference? It should be clarified in detail. In the conclusion section, where are the average error of 4.18% and average optimization rate 9.27% from? The result of how to calculate should be clarified.

Author Response

1. In Section 1, the third paragraph, the author said “the intelligence and automation level of most intersections cannot meet the requirements”, how do we understand this conclusion about intelligence? Does it contradict with the conclusion of this manuscript?

Thank you very much for your suggestion, we have revised this stastement, which is now specifically written as ‘Up to now, intelligent methods such as deep learning [2][3], fuzzy control theory [4][5] and intelligent algorithms [6][7] are proposed, which highly rely on high-precision and real-time traffic data to ensure the reliability. Some scholars believe that using these methods to solve congestions will become the main trend in the future. However, the current intelligence and automation level of most intersections cannot meet the requirements. In fact, more than 90% of the intersections in China are still not equipped with modern detectors such as video detectors and radar detectors [8], so the methods above are not applicable at this stage.’

 

2. As an international journal, the author does not need to emphasize which one is domestic, which one is overseas, they all international scholars working in this field.

Thank you very much for your suggestion. We have revised the Literature Review section according to you advise.

 

3. In Section 1, the author said two main contents of this manuscript are minimum green time calculation modeling and maximum green time calculation modeling, why? Why does the author have to discuss these two parameters? What are the difference between them? The research necessity should be clear in Introduction part, which can help the reviewer understand the target and contribution of this manuscript.

Thank you very much for your suggestion. We have clear this research necessity in the Introduction section, which is now specifically written as ‘Considering the above problem, this paper pays attention to the actuated signal control, an effective and widely used control strategy, relying on traffic detectors to detect traffic flow and make corresponding control decisions [9]. In the actuated con-trol, the minimum green time ensures all queued vehicles dispersion, and the maxi-mum green time limit the maximum time of the phase. These two basic parameters can avoid secondary queuing of vehicles and the green time waste, so it is of great signifi-cance to optimize their value. Furthermore, in view of the current intelligent trans-portation development level in China, further exploration in the actuated control op-timization can highly compatible with the realistic needs.’

 

4. In Section 3, the content and variables definition in the third paragraph is inconsistent with the marks and contents of Fig.1b.

We are very sorry about this problem. We have double checked the part you mentioned, but we didn't find the problem you raised.

 

5. What does y_i mean in equation 16?

We are very sorry about this problem, and it's our negligence. We have added the definition of y_i in the paper, which is now specifically written as ‘Where y_i is flow ratio in flow direction i, which equals to saturated flow divides q_i.’

 

6. Passive voice is generally used in technical papers. Thus, the voice of some sentences needs to be modified, such as the sentence above the Eq.17.

We are very sorry about this problem, and it's our negligence. Now we have revised the relavant statements in this paper. Thank you again for your careful examination.

 

7. In section 4, the author established an optimization model for the maximum green time according to the NEMA phase structure, but the reason and applicability does not have any discussion. Moreover, as the most research work in this manuscript, besides application this existing phase schemes, what is the main contribution of this manuscript, it should be highlighted throughout the paper.

Thank you very much for your suggestion. We now have added the reason and applicability for adopoting NEMA phase structure, which is now specifically written as ‘When considering the influence of phase schemes, this study adopts NEMA phase structure [31]. Since its structure can be flexibly adjusted, such as phase 1 and phase 5 shown in Table 1, it has better adaptability to different traffic situations.’ Besides, we summary our main contributions at final, which is now specifically written as ‘In summary, this paper propose two basic parameter optimization models of ac-tuated control, and verifications successfully prove their validity of improving green time utilization, reducing vehicle delay and enlarging traffic capacity, which is essen-tial in improving traffic sustainability.’

 

8. In section 4, according to the equation 15, as for the second objective, whether the traffic flow capacity in other directions perpendicular to this traffic flow should also be included in the objective function in overall traffic system view?

Thank you very much for your suggestion. The traffic flow in other directions will have an impact in the actuated control. We believe that excessive green time in one direction will lead to increased vehicle delay and reduced traffic capacity in other directions. Thus, this paper proposes the objective function (15), aiming to limit the excessive green time. Table 7 shows the optimization effect which proves the effectiveness of the model.

 

9. What does the variables mean in the first column of Table 5?

We are very sorry about this problem, and it's our negligence. We have added the definition of the variables in the first column of Table 5 in the paper, which is now specifically written as ‘Note: SB represents the south bound direction, NB represents the north bound di-rection, WB represents the west bound direction, EB represents the east bound direc-tion, TH represents the straight through vehicle, and LT represents the left turn vehicle.’

 

10. Why do the optimization ratio results shown in Table 7 have big difference? It should be clarified in detail. In the conclusion section, where are the average error of 4.18% and average optimization rate 9.27% from? The result of how to calculate should be clarified.

We are very sorry about this problem, and it's our negligence. Firstly, we explain the meaning of the average error and the average optimization rate in the last row of the table separately. And then we analyze the reason why the optimization ratio results shown in Table 7 have big difference, which is now specifically written as ‘We can see from the table that under phase schemes F1, F2, F3, the optimization ra-tios all exceed 10%. Under phase scheme F4, since there are only two green time pa-rameters that can be adjusted, it also has an optimization ratio of 2.10%.’

Author Response File: Author Response.pdf

Reviewer 3 Report

Considering the present state of traffic flows in cities, studies about methods for improvement of this are welcome. Traffic lights are in most of the cases the first inconvenient for traffic flow, generators of traffic congestion problems. Intelligent traffic lights maybe seen as a problem solving. 

Anyway, all proposed solutions must be reported to the traffic wave. A well done analysis of, can lead to proper solutions. 

The authors approach is good, but can be improved considering different periods related to the traffic flow.

Considering the study developed into the paper, conclusions can be improved, including specialized authors opinions on results efficiency.

The English language required minor spell check. 

Author Response

1. Anyway, all proposed solutions must be reported to the traffic wave. A well done analysis of, can lead to proper solutions..

Thank you very much for your suggestion. Firstly, we add some analysis of simulation verification results, which is now specifically written as ‘Since we use the improved traffic wave model to calculate queue length, it can be seen from the table that the minimum green time calculation model proposed in this paper (4.18% average relative error) is more accurate than the traditional HCM calcu-lation model (10.44% average relative error) under different queue lengths, which ver-ifies the effectiveness and accuracy of the model.’ ‘We can see from the table that under phase schemes F1, F2, F3, the optimization ra-tios all exceed 10%. Under phase scheme F4, since there are only two green time pa-rameters that can be adjusted, it also has an optimization ratio of 2.10%.’ And then, we revise the Conclusion section to highlight our contributions, which is now specifically written as ‘It can be seen that compared with previous studies, this paper focuses on the in-fluence of queued vehicles, and two basic control parameters, the minimum green time and the maximum green time, are optimized to achieve better control effect. Through this study, more reasonable control parameters can be obtained, so as to avoid green loss, reduce vehicle delay and improve traffic operation sustainability.’ ‘In summary, this paper propose two basic parameter optimization models of ac-tuated control, and verifications successfully prove their validity of improving green time utilization, reducing vehicle delay and enlarging traffic capacity, which is essen-tial in improving traffic sustainability.’

2. The authors approach is good, but can be improved considering different periods related to the traffic flow.

Thank you very much for your suggestion. This paper mainly focus on unsaturated flow, the cycle period that all vehicles queued in the previous cycle have completely released, which means that the traffic flow characteristics are not disturbed by other periods. If the traffic flow is over-saturated, we believe that there exsit problem in the overall operation of the intersection, which cannot be solved only by adjusting the minimum green time. Other methods are needed, such as expanding cycle length, adjusting phase structure, and shortening the green time in other directions. So in this study, we just focus on current cycle periods.

3. Considering the study developed into the paper, conclusions can be improved, including specialized authors opinions on results efficiency.

Thank you very much for your suggestion. We have revised the Conclusion section to highlight our contributions, which is now specifically written as ‘It can be seen that compared with previous studies, this paper focuses on the in-fluence of queued vehicles, and two basic control parameters, the minimum green time and the maximum green time, are optimized to achieve better control effect. Through this study, more reasonable control parameters can be obtained, so as to avoid green loss, reduce vehicle delay and improve traffic operation sustainability.’ ‘In summary, this paper propose two basic parameter optimization models of ac-tuated control, and verifications successfully prove their validity of improving green time utilization, reducing vehicle delay and enlarging traffic capacity, which is essen-tial in improving traffic sustainability.’

4. The English language required minor spell check.

Thank you for your careful examination, and this is really our problem. We have checked the English grammar again and again, and hopelly it doesn't bother you with reading.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

This present form of the manuscript can be considered for publication in Sustainability Journal.