Estimation of Vehicle Traffic Parameters Using an Optical Distance Sensor for Use in Smart City Road Infrastructure

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper presents a low-costs roadside traffic detection device that detects vehicles by inspecting the return distance of a single beam radiowave. Although the study is comprehensive and explored many aspects and performance-impacting factors of the proposed sensor, here are the main limitations:

1. The literature review on existing traffic sensors is quite insufficient. There are many or more equally cost-efficient solutions with better capabilities such as computer-vision based, radar, microwave, on pavement loop detector, traffic tubes, and pucks. 

2. There are critical issues with the proposed sensor and sensor setup that will limit its usability in traffic data collection. In essence, this is a presence detector and its detecting efficiency is heavily impacted by occlusion. Only traffic from the right-most lane can be effectively detected. The partial detection in multi-lane situation really makes this sensor inferior to many existing traffic detection solutions. Computer vision based method with cheap HD camears and open-source ultralytics algorithm can not only gather all traffic data but also classifications and trajectories.

3. There is a large gap between the proposed sensor capabilities and Smart City solutions due to its limited data outputs (right-most lane volume only, no speed, no classification, no lane-by-lane volume, no trajectories). The writing should tune down on related descriptions.

4. The authors can look into some existing literatures on vehicle-reidentification by matching return signal patterns between a pair sensor stations. This can help potential provide travel time/speed information.

Comments on the Quality of English Language

The overall english write is adequate. Some additional proofreading and shortening of non-technical sections may be needed.

Author Response

We would like to express our gratitude for your comments. We have carefully considered each of your remarks and striven to address them individually (in attachment). We hope that the manuscript has been improved as a result. We have incorporated changes in the manuscript in response to the comments and have indicated their location in the manuscript (page number, section number). Additionally, we have highlighted the changes in the manuscript.

The reviewers' comments have been taken into account and incorporated into the text in the following colours:

• Reviewer 1, blue
• Reviewer 2, brown
• Reviewer 3, orange
• Reviewer 4, green

However, in instances where an answer has been provided that is identical to a comment made by another reviewer, the colour code for the first reviewer in the sequence is maintained.

Corrections in English are highlighted in red.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This is a field test work that could have merit if properly discussed and presented.

The merit of the proposed solution compared to other traffic sensors seems to be centred on the cost effectiveness of the optical distance sensor. If this is so, a performance analysis that contrasts the cost and performance of mainstream solutions (magnetic sensors, radar, cameras) should be presented and an comparison of emerging technologies (lidar, distributes acoustic sensors) should be provided.

The proposed method seems to detect the number of passing vehicles and their category (not type) - how about the speed, the occupancy, the load? how does number and category data inform intelligent transportation systems? what is the added value here?

the presentation of the measurements, results, and related discussion lack clarity (see attached for details). The authors claim that a patent application is filed, not clear what is the novelty here? this is a setup of existing sensors and processors.

 

Comments for author File: Comments.pdf

Comments on the Quality of English Language

This is OK, figures and table need to be significantly improved as in the attached

Author Response

We would like to express our gratitude for your comments. We have carefully considered each of your remarks and striven to address them individually (in attachment). We hope that the manuscript has been improved as a result. We have incorporated changes in the manuscript in response to the comments and have indicated their location in the manuscript (page number, section number). Additionally, we have highlighted the changes in the manuscript.

The reviewers' comments have been taken into account and incorporated into the text in the following colours:

• Reviewer 1, blue
• Reviewer 2, brown
• Reviewer 3, orange
• Reviewer 4, green

However, in instances where an answer has been provided that is identical to a comment made by another reviewer, the colour code for the first reviewer in the sequence is maintained.

Corrections in English are highlighted in red.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Abstract:

The abstract should not be written in points. The authors write it in the form of 3 points, this should be a merged paragraph. It is unclear what the authors mean by the following: "The use of different sensor types, such as infra-red or acoustic, will be presented in subsequent publications."

Introduction:

The first introduction section that discusses several aspects of traffic dynamics as well as spatial distribution etc. does not really give an impactful discussion to the problem being addressed. This needs to be clearly written in terms of the objectives of the article. The key objective being traffic flow optimisation and traffic engineering, then these should be discussed as a problem first before describing the contributions. There is no mention of currently used technologies, but straight jumps into optical sensors for measurement of road traffic flow.

Materials and Methods:

Prior to going into the how the system is developed, there needs to be an extensive survey of current state-of-the-art technologies that exist within the automotive industry as well as academic articles. The description of the system devised is ok, however, it is not clear why the system is connected via a serial port instead of wireless communications - for example, there would be not a possibilty on road networks for the devices to be connected via serial ports.  Using a sensor with 100cm = 1m to 550cm = 5.5m and loss in accuracy, does not cleary demonstrate the effectiveness of the sensor. 

How is the calibration performed? There is no mention of this.

Field Experiments and Results:

Only one sensor being deployed or a network of multiple sensors across the road? How can one sensor determine the traffic flow characteristics?

How does the system work for a long stretch of road and bottleneck traffic at the road ahead? It aids in counting of cars and traffic profiling, but it does not provide a clear picture for a long stretch of the road. 

Overall, the study is quite comprehensive in terms of the results presented and the data collected, however it does not justify for long-range or even classification of the vehicle types. 

The conclusions and future enhancements are also well established and there is quite a bit of merit, but it feels like the entire article is written about a single sensor (Sharp) and its impact on traffic data collection and then visualised for several aspects.

 

 

 

 

General Comments: The flow of the article needs to be reconsidered and written in a better logical flow manner. Also, there are sections, where the font size constantly changes, for example in introduction, before and after the figure 1. Likewise, in section 2, again after figure 2, the font size is reduced. There needs to be clear, consistent font size in the entire article.

 

Comments on the Quality of English Language

English needs extensive corrections, there are numerous sentences that are just 6-7 words long and these could be combined with other sentences prior or post writing those short sentences.

Author Response

We would like to express our gratitude for your comments. We have carefully considered each of your remarks and striven to address them individually (in attachment). We hope that the manuscript has been improved as a result. We have incorporated changes in the manuscript in response to the comments and have indicated their location in the manuscript (page number, section number). Additionally, we have highlighted the changes in the manuscript.

The reviewers' comments have been taken into account and incorporated into the text in the following colours:

• Reviewer 1, blue
• Reviewer 2, brown
• Reviewer 3, orange
• Reviewer 4, green

However, in instances where an answer has been provided that is identical to a comment made by another reviewer, the colour code for the first reviewer in the sequence is maintained.

Corrections in English are highlighted in red.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

Many different distance sensors are used to collect various traffic data, including 359 road traffic. The use of ultrasound sensors is highly prevalent within the literature, for 360 example, see [24–26]. In addition, light detection and ranging (LIDAR) sensors are becom-361 ing increasingly popular for the collection of traffic data [27–29]. Ultrasonic sensors are 362 very cheap and widely available, but unreliable due to the multifarious shapes and color 363 schemes of vehicles, which can cause substantial interference [29, 31]. Although less sus-364 ceptible to interference, LIDAR sensors remain expensive. The cheapest short-range, lin-365 ear LIDAR sensors cost more than €100. 366 

Low-cost sensors are ideal for use in urban smart city infrastructure, and can aid the 367 operation of such cities. Smart cities are designed to embody flexibility, innovation, and 368 creativity. The former aspect is particularly relevant for this study: flexibility can be un-369 derstood as the city's ability to adapt quickly to changes in internal and external condi-370 tions. This includes rapid adaptation of the city road infrastructure, and the organization 371 thereof, to observable changes in traffic dynamics. Central to the concept of a smart city is 372 the use of information and communication technologies. As such, the use of a network of 373 low-cost distance sensors to measure traffic parameters is appropriate. The objective of 374 this system is to improve the mobility of the city inhabitants, by improving road travel 375 [32–39]. Hence, this study proposes to equip the road network with the low-cost sensors 376 described above. These sensors should not only be located in discrete sections of the net-377 work, but distributed throughout the entire network, to enable continuous monitoring of 378 road traffic processes. 

 

Author Response

We would like to express our gratitude for your comments. We have carefully considered each of your remarks and striven to address them individually (in attachment). We hope that the manuscript has been improved as a result. We have incorporated changes in the manuscript in response to the comments and have indicated their location in the manuscript (page number, section number). Additionally, we have highlighted the changes in the manuscript.

The reviewers' comments have been taken into account and incorporated into the text in the following colours:

• Reviewer 1, blue
• Reviewer 2, brown
• Reviewer 3, orange
• Reviewer 4, green

However, in instances where an answer has been provided that is identical to a comment made by another reviewer, the colour code for the first reviewer in the sequence is maintained.

Corrections in English are highlighted in red.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thanks for the authors' responses. Overall, I think there is some merit in developing this sensor, but the authors should make a balanced statement on its pros and cons. 

 

1. Cost comparison: For traffic sensors system to work 24x7 in the field on rugged packaging, chip upgrading, and weather proofing, mounting configuration, edge and central applications. These are significant cost to bring a experimental sensor prototype to production-ready devices and solutions.

 

2. Comparison to video, RTMS, and other prevailing sensors. The authors proposed mounting the sensors to overhead gantries to improve the multi-lane detection capabilities to match the capability of one video or prevailing roadside sensors. Such a setup is not a fair comparison on the cost side. There are significant construction and maintenance costs involved in installing multi-lane sensor arrays. Yes, the sensors may still be cheap or comparable HD camera lenses. The associated construction and maintenance costs for the overhead configuration will be so significant that the sensor cost is negligible. The reviewer is not looking for a "magic" change or setup for the proposed sensor to achieve certain capabilities already fulfilled very well by existing sensors. The reviewer seeks objective statements from the authors regarding the sensor's pros and cons and acknowledges the limitations in practical applications. The authors should also provide objective comparisons on the pros and cons with the existing sensors. No need to overly extraggery the distadvantage of the existing sensors while not presenting fully their advantages. They are not cost-prohibitive in practice since they have been deployed in millions all over the world. Again the cost of the sensor is just a fraction of the cost when deploying sensing technologies in the field.

 

3. Lines 100-104, Page 3. Please remove the sentences on overhead sensor setup. These capabilities of detecting trajectories and classifications are not validated with the experimental results presented in this study. This is future work.

 

4. Satellite imagery and are relatively irrelevant to this study since the focus is the roadside sensors. The following is a classic document and it seems that the authors may need to do some reading to get more holistic and objective view on traffic detection and existing technologies. https://www.fhwa.dot.gov/publications/research/operations/its/06108/06108.pdf

https://www.fhwa.dot.gov/publications/research/operations/its/06139/06139.pdf

 

5. One more technical issue: See if the authors can clarify if they have validated the accuracy of multi-lane detection results, especially when occlusion occurred. Are there any ground truth data (e.g. traffic video) collected to analyze the error scenarios.

Comments on the Quality of English Language

Some additional proofreading may be needed on the revised portion of the paper.

Author Response

Please see the attachment

Please find enclosed the revised manuscript entitled "Estimation of Vehicle Traffic Parameters Using an Optical Distance Sensor for Use in Smart City Road Infrastructure" that we would like to be considered for publication in the Journal of Sensor and Actuator Networks, 2024.

Please find also a letter explaining the changes made in response to the comments and suggestions that we received.

We appreciate for your precious time in reviewing our manuscript and providing valuable comments. It was your valuable and insightful comments that led to possible improvements in the current version. Below we provide the point-by-point responses. All modifications in the manuscript have been highlighted in: (light) blue, red, orange and green.

We have made a concerted effort to adequately respond to each suggestion received from the reviewers. We firmly believe that the reviewer’s comments and suggestions have significantly improved this manuscript. We do hope that you and the reviewers find this manuscript acceptable for publication in the Journal of Sensor and Actuator Networks, 2024.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

the authors have responded to the main comments with sufficient details.

this reads like a well written report with clear objectives and not like a research paper.

Comments on the Quality of English Language

good english

Author Response

Please see the attachment

Please find enclosed the revised manuscript entitled "Estimation of Vehicle Traffic Parameters Using an Optical Distance Sensor for Use in Smart City Road Infrastructure" that we would like to be considered for publication in the Journal of Sensor and Actuator Networks, 2024.

Please find also a letter explaining the changes made in response to the comments and suggestions that we received.

We appreciate for your precious time in reviewing our manuscript and providing valuable comments. It was your valuable and insightful comments that led to possible improvements in the current version. Below we provide the point-by-point responses. All modifications in the manuscript have been highlighted in: (light) blue, red, orange and green.

We have made a concerted effort to adequately respond to each suggestion received from the reviewers. We firmly believe that the reviewer’s comments and suggestions have significantly improved this manuscript. We do hope that you and the reviewers find this manuscript acceptable for publication in the Journal of Sensor and Actuator Networks, 2024.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have made substantial changes to the manuscript based on the comments provided earlier.

The background study of current technologies and sensors has been well-established now with the table 1.

 

However, the changes are not adequate enough.

For example comment: "How does the system work for a long stretch of road and bottleneck traffic at the road ahead?" 

has not been substantially detailed enough. Also, the discussion on single sensor and its impact is also not well-established, despite the comments.

Overall, I believe that there is still some additional work that needs addressing.

 

Comments on the Quality of English Language

There is substantial effort put in enhancing the readability of the article.

Author Response

Please see the attachment

Please find enclosed the revised manuscript entitled "Estimation of Vehicle Traffic Parameters Using an Optical Distance Sensor for Use in Smart City Road Infrastructure" that we would like to be considered for publication in the Journal of Sensor and Actuator Networks, 2024.

Please find also a letter explaining the changes made in response to the comments and suggestions that we received.

We appreciate for your precious time in reviewing our manuscript and providing valuable comments. It was your valuable and insightful comments that led to possible improvements in the current version. Below we provide the point-by-point responses. All modifications in the manuscript have been highlighted in: (light) blue, red, orange and green.

We have made a concerted effort to adequately respond to each suggestion received from the reviewers. We firmly believe that the reviewer’s comments and suggestions have significantly improved this manuscript. We do hope that you and the reviewers find this manuscript acceptable for publication in the Journal of Sensor and Actuator Networks, 2024.

Author Response File: Author Response.pdf