# Study on Representative Parameters of Reverse Engineering for Maintenance of Ballasted Tracks
## 3 Representative Parameters for Ballasted Track  
### Maintenance Standards for Ballasted Track  
Generally, a ballasted track is referred to as \"classical track\" or \"conventional track\" and has been in use longer than concrete track [24]. The term \"ballasted track\" is used in the International Union of Railways (UIC) Leaflet 719 [25]. The core structure of this ballasted track is composed of rails, fastenings, sleepers, the ballast bed, sub-ballast, and subgrade [24], as shown in Figure 3.  
Ballasted tracks have the advantages of a higher elasticity and easier track correction than non-ballasted track treatment but require continuous track management, such as regular repair and correction work. This routine track management implies that ballasted tracks have a higher risk of accidents, such as train derailments, compared to non-ballasted tracks, requiring routine maintenance to limit life cycle cost (LCC). Particularly, compared to non-ballasted tracks, ballasted tracks require routine maintenance because of frequently occurring track irregularities, ballast refills, and sleeper irregularities. For this reason, countries such as EN (European Union), France, Germany, Italy, and Austria, the United States, and Japan perform intensive routine maintenance of ballasted tracks, using detailed acceptance criteria for track irregularities. The German rail infrastructure company, DB Netz AG, make to manage the operation with detailed railroad maintenance standards [26]. DB Netz AG's \"Track Maintenance Standard\" provides acceptance criteria for track irregularities according to speed by classifying maintenance activities according to longitudinal level adjustment, twist, height adjustment, and lining. The EURO Code provides completion criteria for track irregularities in new installations and improvements to tracks [27]. The EURO Code present criteria for track gauge, cross-level, track surface, alignment, and twist. The French national state-owned railway company, SNCF, presents track management standards for track lines that consider train operation safety and comfort. The SNCF classifies management criteria considering track gauge, track surface, alignment, cross-level, and flatness and presents different detailed management criteria based on train speed [27; 28]. Italy classifies management items by track gauge, alignment, track surface, cross-level, and twist and provides detailed management criteria based on train speed [27]. Austria classifies track management items according to track surface, cross-level, alignment, twist, and track gauge and provides detailed management criteria based on train speed [27]. The American Public Transportation Association in the US provides standards for ballasted track maintenance on \"Rail Transit Track Inspection and Maintenance (2017)\" [29]. Particularly, the US standards classify track management items according to track gauge, cross-level, track surface, and alignment, like those of other countries. In addition, they use superelevation as a classification item, and their management standards are subdivided in detail according to train speed. For  
Figure 3: Cross-sectional diagram of the ballasted track. conventional tracks in Japan, track maintenance guidelines are classified according to track gauge, cross-level, track surface, alinement, and flatness, and detailed criteria are presented according to train speed [29]. In Republic of Korea, the Korea National Railway's \"Track Maintenance Guide (2016)\" presents maintenance criteria for general railroads [30]. Similar to the standards of other countries, the Track Maintenance Guide presents detailed routine maintenance criteria based on track gauge, cross-level, level adjustment, and alignment. The Korean maintenance standards present detailed management criteria for ballast refill and sleeper irregularities for ballasted track, in addition to criteria for major management items, such as track gauge, cross-level, level adjustment, and alignment.