## 5 Conclusions  
This study concludes with the following:  
* Although there are some minor differences between the structure of the two most common last-mile delivery vehicle models used in Korea, the results indicated no statistically significant difference in the vertical vibration levels between them. Therefore, a composite vibration test profile developed in this study could be used interchangeably between both vehicle models.
* The vertical vibration levels observed from the most common last-mile delivery vehicles in the U.S. and Hungary and the international test standard for pickup and delivery of parcels were both higher than the vibration levels measured on last-mile delivery vehicles in Korea; hence, the recommended vertical vibration test spectrum for Korea is lower. However, various factors, like road and driving conditions, could also affect the level of parcel delivery vehicle vibrations in different geographical regions. Therefore, further studies are needed to understand whether it is the quality  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Frequency Range** & **ISTA 3A (Grms)** & **Recommended (Grms)** & **Intensity** **(Compared in the \%** **of Standard)** \\ \hline
1–4 Hz & 0.244 & 0.078 & \(\sim\)68\% \\
4–15 Hz & 0.146 & 0.056 & \(\sim\)62\% \\
15–24 Hz & 0.095 & 0.074 & \(\sim\)22\% \\
24–50 Hz & 0.063 & 0.056 & \(\sim\)11\% \\
50–200 Hz & 0.343 & 0.181 & \(\sim\)47\% \\ \hline \hline \end{tabular}
\end{table}
Table 4: The overall Grms differences in various bandwidths.  
of roads and driving conditions or the vehicle type itself that causes more differences in vibration levels.
* The highest intensity peak for the recommended vibration test spectrum was in a lower frequency band (1.5 to 2 Hz) than the ISTA 3A pickup and delivery vibration test spectrum (3 to 4 Hz). This result suggests that packaging engineers in Korea should avoid designing packaging systems with natural frequencies overlapping or close to the peak intensity frequency band unique to the Korean delivery environment rather than avoiding the peak intensity frequency bands indicated in the international test standard.
* The PD levels of last-mile delivery vehicles in Korea were lower than were recorded in Hungary with no time compression in the entire frequency range that was an interest of this study (1 to 200 Hz).
* A simplified, recommended vertical vibration test profile for last-mile delivery in Korea could help packaging engineers in Korea test their packages in the laboratory before shipping them without processing the large datasets that are provided in ready-to-use form in this study.  
Conceptualization, S.K. and L.H.; data curation, S.K.; formal analysis, S.K.; funding acquisition, L.H.; investigation, S.K.; methodology, S.K. and L.H.; project administration, L.H.; resources, L.H., S.L. ([PERSON]) and S.L. ([PERSON]); software, S.K.; supervision, L.H.; validation, S.K. and L.H.; visualization, S.K.; writing--original draft, S.K.; writing--review and editing, L.H., S.L. ([PERSON]) and [PERSON] ([PERSON]). All authors have read and agreed to the published version of the manuscript.  
This research was funded by CJ CheilJedang.  
Not applicable.  
Restrictions apply to the availability of these data. Data were obtained from CJ CheilJedang and are available from the authors with the permission of CJ CheilJedang.  
The authors acknowledge access to facilities and vehicles provided by CJ Logistics.  
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Author [PERSON] is employee of CJ Logistics, Author [PERSON] is employee of CJ CheilJedang, who provided funding/technical support for the work. The funder had no role in the design of the study; in the collection, analysis, or interpretation of data, in the writing of the manuscript, or in the decision to publish the results.