## 3 Method and Materials
### Interview Results and Discussion  
This subsection presents the results of qualitative data analysis. The researchers used NVivo pro12 software to analyze the interview records to improve the efficiency and accuracy of the analysis. The interview process allowed a detailed understanding of the goals and obstacles of asphalt concrete pavement monitoring to be ascertained. It was also possible to discuss and analyze the benefits and improvement options enabled by implementation of monitoring systems in asphalt pavement. (1) Objective of the system  
The interviewee (A1) said that the current asphalt pavement generally does not reach the designed service life, and major damages such as ruts, cracks, and oil flooding will occur within 3-4 years of use, which seriously affects the comfort and safety of daily use. Therefore, maintenance needs to be carried out, resulting in a waste of funds. Therefore, it is necessary to monitor the construction of asphalt pavement to improve the quality of the pavement and reduce losses. Respondents (A19) said that the early damage to asphalt pavement was also related to many external factors, such as overloaded vehicles, bad weather, and complex geology. However, in most cases, the road surface was damaged due to technical reasons. For example, in the production process, the proportion of asphalt mixture was unbalanced, the stirring speed was not up to standard, and the mechanical operation was not in place. There were problems with the quality of the road surfaces. Therefore, the primary goal of monitoring must be to improve the construction quality of asphalt pavement and build high-quality asphalt concrete pavement. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Interview Outline** & & **Node Encoding in Nvivo** \\ \hline \multirow{4}{*}{
\begin{tabular}{c} Asphalt road digital \\ monitoring test \\ demand analysis \\ \end{tabular} } & 1. What is the goal of digital monitoring of asphalt pavement? & Q1 \\  & 2. What are the difficulties in implementing monitoring at present? & Q2 \\  & 3. How is the monitoring of the asphalt mixture carried out? & Q3 \\  & 4. In the process of monitoring the asphalt mixture, what’s the & Q4 \\  & problem? How to solve it? & Q5 \\  & 5. At present, what are the difficulties in the collection and & Q5 \\  & transmission of monitoring data? & Q6 \\  & 6. What are the difficulties encountered in the application of the & Q6 \\  & existing monitoring system? & Q7 \\  & 1. What functions do you want the system to have? & Q8 \\  & 2. What are the requirements for data transmission? & Q9 \\  & 3. What are the benefits of using a monitoring system? & Q10 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Interview outline. Obstacles for system implementation  
Barriers are challenges or limitations that hinder asphalt pavement construction monitoring. For example, after the monitoring data are collected by the sensor, there is a delay in the data transmission and the feedback is not timely, which leads to the failure of the monitoring process [29; 30]. During the interviews, technical issues were identified as the biggest hurdles, including \"scope issues\", \"data transfer\", and \"data processing\". Respondents (A2, A5, A7, A11, A12, A13, and A14) indicated that the current asphalt pavement monitoring process needed to expand the scope of the monitoring system. However, if multiple systems were used for monitoring, the data would not be easily correlated. Respondents (A15, A23, A24, A25) believed that the monitoring data transmission was delayed with the signal often fluctuating due to weather and other reasons, and the data transmission was subsequently slow. Furthermore, respondents (A1, A3, A4, A6, A8, A9, A10, A17, A18, A20) indicated that the processing of monitoring data remained challenging.