Mobile Access Hub Deployment for Urban Parcel Logistics
Round 1
Reviewer 1 Report
This manuscript provides a mathematical evaluation of the concept of mobile hubs in parcel distribution networks. It is a timely topic and I read it with much pleasure. The manuscript provides a fine and clear understanding of the impact of different parameters on this potential last mile solution. I have a set of minor remarks that in my eyes would help readers to draw the correct lessons from this exercise.
My main comment concerns an elaboration of the experiment setting. First, the dimensions of the unit zone are not clear. This is important as the cost calculation depends on the delivery density (δ in eq 2). The nominator of δ is the Economic Load which is computed, yet it is of fundamental importance to understand the area in which this economic load has to be delivered/picked-up, otherwise, it is very difficult to correctly assess the real potential of the mobile hub concept. One can assume it is currently 1km², yet it should be at least stated in table A1. Second, an elaboration of the impact of the last mile vehicle choice would be useful. The authors suggest a similar vehicle as in Figure 1 in line 166. Yet it is unclear why such vehicle is assigned a higher rider speed than the courier in the simulation. 35km/h on average with a tricycle in an urban environment is very high. Local projects with electrically-powered delivery bikes reach 15-20km/h on average. Also the higher GHG emission per km for the rider compared to the courier remains unclear. The same comment can be made for the illustrative case.
While the academic contribution of this paper is clear, and also noted in the conclusion, the elaboration of the description of the settings would help to provide a clearer lesson for all types of stakeholders. Under what kind of real-world context is the described analysis feasible? A reflection on this would be appreciated. For example, 50 deliveries/unit, which seems a minimum requirement in figure 3, is quite a lot. The illustrative case goes in that direction, yet the results could be discussed more critically. For example, the study area is way more compact than the setting in figure 5, and a variation of <1 to almost 1000 parcels per spatial unit is also very significant (what is the median on a daily basis?). A reflection on where such situations could take place, and hence in which context the mobile hub is really feasible, would be an improvement. Similarly, what is the value of using mobile hubs instead of fixed local hubs? The analysis for this is provided in figure 5, yet the question remains how representative a variation of 200% is (e.g. for what time range is the data in line 416?)
Smaller comments:
- some typos and unclear sentences remain, e.g. line 206; line 43-44
- One of the main points in the introduction, that the impact of traffic restriction comes at the expense of environmental sustainability, is quite outdated. More recent work on that topic should be available.
Author Response
We would like to thank the reviewer for the constructive comments and discussions that we believed helped us improve the quality of the paper. We have responded to each point made, and made modifications when necessary in the manuscript (highlighted in blue).
Please see the attachment for our responses.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This paper deals with the interesting topic of the use of mobile hubs for urban parcel logistics. The paper is well-written, methodology clear and supported by the results of the tow case studies (hypothetical and real). However, there are a few points in the paper that still remain unclear to the reader and that should be better described by the authors. Here are my recommendations:
- In lines 188-194 the authors present the parameters used in the economic assessment. It's not clear if driver cost is included in this economic evaluation. Please specify it.
- About the methodology: whatever the positioning of the hubs, is it guaranteed in any case that all areas are served? In other words: is there a maximum waiting time for customers, after which the area is considered "not served"?
- What is the software used to carry out the analyzes in the two case studies?
- Often these type of deliveries in urban areas are made with small and electric vehicles that can have access to roads and areas reserved for pedestrians. Is this factor taken into account when choosing the routes crossed during deliveries in the real case study?
- It would be interesting to include the presence of private vehicle traffic (and therefore of an analysis in different hours of the day) in the evaluation of travel times
Author Response
We would like to thank the reviewer for the constructive comments and discussions that we believed helped us improve the quality of the paper. We have responded to each point made, and made modifications when necessary in the manuscript (highlighted in blue).
Please see the attachment for our responses.
Author Response File: Author Response.docx
