# A Perfect Decomposition Model for Analyzing Transportation Energy Consumption in China
## 4 Conclusions  
A perfect model that decomposes the residual term is proposed on the basis of the Laspeyres Index Decomposition and complete decomposition method. This paper focuses on the residual terms in the exponential decomposition method. The existing complete decomposition model is improved, the improved decomposition model is summarized and deduced in detail, and the unified expression of the decomposition model is derived. The model is applied to build a complete decomposition model of the impact factors of transportation energy consumption in different directions. The decomposition model not only has the advantages of the existing decomposition methods but also can \"perfect\" decompose the remaining items, taking into account the direction of the change of the index influencing factors. This technique makes it possible to present symmetric decomposition without residuals. The perfect method decomposes the residual term completely according to the direction of index change. More accurate calculation results are obtained by comparing Laspeyres and the complete decomposition method. The validity of the perfect model is verified. Lastly, this decomposition model to transportation energy consumption is applied in China and the following conclusions have been drawn.  
Transportation turnover volume is the main influencing factor that determines the main trend of transportation energy consumption. Except for a few years, the contribution rate of transportation turnover volume to transportation energy consumption growth is more than 80%.  
Transportation energy consumption intensity is the main factor for energy savings. From 1985 to 2012, the change of energy intensity saves 84.609 Mtce. Except for a few years, five transportation modes play a key role in energy saving due to their lower energy intensity. Research on energy consumption intensity should focus on reducing energy consumption intensity of highway and aviation.  
The transportation structure adjustment is the key to saving energy and has great potential to save energy. Highways account for absolute advantage. Reducing energy demand is mainly decided by the adjustment of highway transportation structures. Railways play an obvious energy saving role in structure share.  
**Author Contributions:** Conceptualization, Y.Y., X.J. and C.S.L.; methodology, Y.Y. and X.J.; software, Y.Y.; validation, Y.Y., X.J. and C.S.L.; formal analysis, Y.Y., X.J. and C.S.L.; investigation, X.J.; resources, X.J.; data curation, X.J.; writing--original draft preparation, Y.Y., X.J. and C.S.L.; writing--review and editing, Y.Y.; visualization, Y.Y.; supervision, X.J. and C.S.L.; project administration, X.J. and C.S.L.; funding acquisition, X.J. and C.S.L. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Fundamental Research Funds of the National Natural Science Foundation of China (U2034208) and the study of the spatio-temporal tunnel theory for railway transportation organization (04060075), Beijing Jiaotong University, China.  
Not applicable.  
Data Availability Statement: Data is unavailable due to privacy or ethical restrictions.  
The authors declare no conflict of interest.