## 4 Conclusions  
1. BRT asphalt pavement structures are prone to permanent deformation, mainly unstable rutting, during the high-temperature season. The results of this study showed that the possibility of cracking was greater at the bottom of the subbase than at the base, and when the load speed was increased from 10 km/h to 20 km/h and then to 30 km/h, the tensile stress at the bottom of the base and the subbase decreased by 16.1% and 1.3% and by 6.5% and 11.3%.
2. The lower the initial speed of the BRT vehicle, the longer the duration of the vertical compressive stress, tensile stress of the bottom of the layer and shear stress, and the more unfavorable the conditions for the asphalt pavement structure. Considering the duration and peak value of the mechanical response, controlling the BRT operating speed within the 30-40 km/h range could effectively reduce the occurrence and development of permanent deformation of asphalt pavement structures and fatigue cracking and shear failure of the base and subbase.
3. During the high-temperature season, the development of permanent deformation of the BRT asphalt pavement structure occurred in four phases: compaction, flow and rearrangement, accelerated accumulation, and stability. Permanent deformation of the BRT asphalt pavement structure mainly occurred from 11:00 to 18:00. Compared to the frequency of BRT vehicles, temperature had a greater influence on the permanent deformation of asphalt pavement. Reducing the sensitivity of pavement to high temperatures could effectively improve the ability of asphalt pavement to resist rutting.
4. The depression and uplift deformation values of the upper, intermediate and lower layers decreased with increasing vehicle speed, and the deformation values of the intermediate layer were the largest at the different driving speeds. When the speed increased from 10 km/h to 40 km/h, the rut depth decreased by 32%. To delay the initiation and development of rutting, special attention should be given to the ability of the intermediate layer to resist deformation while reasonably increasing the vehicle speed.  
In addition to the above conclusions, more in-depth studies are suggested, focusing on the mechanical characteristics of BRT asphalt pavement structures in low temperatures. It is recommended that further investigation through the use of pilot road sections and periodical performance assessment be carried out before the results are made directly applicable to practitioners.  
Figure 19: Variation in permanent deformation of each structural layer with vehicle speed: (**a**) depression deformation; (**b**) uplift deformation.  
**Author Contributions:** Conceptualization, Y.W.; methodology, Y.Z.; validation, Y.W.; writing--original draft preparation, Y.W.; writing--review and editing, Y.Z.; visualization, Y.W. All authors have read and agreed to the published version of the manuscript.  
This study was supported by the Science and Technology Planning Project of Gansu Province (20 JR10 RA261) and the Young Scholars Science Foundation of Lanzhou Jiaotong University (2018013).  
Not applicable.  
**Acknowledgments:** Special thanks are due to [PERSON] from China Railway Design Corporation for contributing to the software and formal analysis.  
The authors declare no conflict of interest.