Travel Time Reliability Analysis Considering Bus Bunching: A Case Study in Xi’an, China
Round 1
Reviewer 1 Report
Travel Time Reliability Analysis Considering Bus Bunching: A Case Study in Xi’an, China
Authors have presented topical research on the efficiency of public transport operations. Authors believe that bus bunching occurring at stops has an unstable impact on bus travel time. In such a sense, the authors build the rationale for this research with the argument that due to the occurrence of the bus bunching, the dwell time at stops in the entire bus travel dramatically deviates from the timetable, which reduces the reliability of the bus travel time. In order to evaluate urban bus travel time effectively, the travel time reliability (TTR) addressing bus bunching should be analyzed. Therefore, the study aims to develop an evaluation model to analyze the TTR of urban buses considering bus bunching to improve the evaluation and estimation of bus travel time. The proposed model is used to analyze 113 runs of a bus route in Xi'an city, China. Real-time GPS data are used to analyze the operation of each run from the origin to the destination stops. Results show that 74.34% of the runs are delayed. In addition, the number of stopping routes at peak periods significantly impacts the occurrence of bus bunching. Overall, this research considers microscopic factors for bus travel time reliability evaluation and could effectively make results. Moreover, this research can provide guidance for bus operating companies and city government departments to reduce the occurrence of bus bunching frequently from these two aspects: the more suitable timetables and the more reasonable the number of stopping routes in urban center area.
Authors have well-built the study rationale and background with literature and related studies. Authors are encouraged to add the Literature section heading separately. The research has used sound methods, experiments and analysis techniques. The conclusions section requires the author's attention. Authors are advised to explain the inferences in detail and according to the referenced literature of TTR. Also, add how the study inferences are distinct from previous literature. Moreover, in the Conclusion section, each research contribution should be mentioned in bullet points with justification. Study limitations should also be added along with future recommendations.
Author Response
Dear reviewer,
Thank you for your nice comments on our work.
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
There are fruitful research achievements of analyzing the causes and impacts of bus bunching and travel time reliability as well as strategies for reducing bus bunching. New methodologies are expected to alleviate bus bunching and improve travel time reliability concerned with improvement of bus service level.
Author Response
Dear reviewer,
Thank you for your nice comments on our work.
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
- author information must/should include department information.
- the introduction section is too big. try to describe the definition of bus bunching in a separate section/sub-section.
- what are the particular research questions?
- who will benefit from this research? citizens? other researchers? in what ways?
- why is the travel time divided into two parts? why is this helpful to the Xi'an case?
- what is special and interesting and challenging about the Guanzhong plain?
- what is the procedure for collecting data?
- how is this research relevant to the UN sustainable development goals?
- how can we expand this Xi'an experience and practice to other cities, e.g., Paris, New York?
- please include more references.
Author Response
Dear reviewer,
Thank you for your nice comments on our work.
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
It is good to see that the manuscript has been improved in the second version. There are still some typos in the manuscript, e.g. line 459, 461.
