Summary of evaluation indicators
| No | Geometry index | Developer | Parameters | Advantage | Disadvantage | Year |
|---|---|---|---|---|---|---|
| Objective (single) track quality indices | ||||||
| 1 | Standard deviation (BSI Group, 2010) | Europe standard (EN 13848–5) | General method covering various geometry parameters | Cannot measure superposition effect of irregularities | 1981 | |
| 2 | K value (Khouy, Larsson-Kråik, Nissen, Juntti, & Schunnesson, 2014) | Sweden National Railway | Total length of the track with deviations below comfort limits | The irregular length of track can be measured |
| 2002 |
| 3 | Q (Sadeghi, 2010) | Sweden National Railway | Combination of alignment, gauge and cant | Covers cant, gauge, alignment irregularities |
| 2002 |
| 4 | Length-based TQI (El-Sibaie & Zhang, 2004) | US railway | Traced length of space curve | Measures irregular longitudinal length |
| 2005 |
| Objective (combined) track quality indices | ||||||
| 5 | W5 (Sadeghi, 2010) | Austrian Railway | ☑ Longitudinal level | Considers correlation among five geometry parameters | Ignores parameter weights | 2000 |
| ☑ Alignment | ||||||
| ☑ Gauge | ||||||
| ☑ Cant | ||||||
| ☑ Twist | ||||||
| 6 | MDZ (Lyngby, 2009) | – | ☑ Longitudinal level | Passenger-centric; focuses on acceleration change over distance |
| 2002 |
| ☑ Alignment | ||||||
| ☒ Gauge | ||||||
| ☑ Cant | ||||||
| ☒ Twist | ||||||
| 7 | R2 (Sadeghi, 2010) | American | ☒ Longitudinal level | Comprehensively considers alignment, gauge, cant |
| 2003 |
| ☑ Alignment | ||||||
| ☑ Gauge | ||||||
| ☑ Cant | ||||||
| ☒ Twist | ||||||
| 8 | TQI (Sadeghi and Askarinejad, 2010) | Chinese National Railroad | ☑ Longitudinal level | Describes deterioration from statistical & physical perspectives | Ignores wavelength-dependent effects on vehicle (comfort, derailment) | 2003 |
| ☑ Alignment | ||||||
| ☑ Gauge | ||||||
| ☑ Cant | ||||||
| ☑ Twist | ||||||
| 9 | J (Sadeghi, 2010) | Polish Railway | ☑ Longitudinal level | Weighted average with lower weight for vertical irregularities |
| 2005 |
| ☑ Alignment | ||||||
| ☑ Gauge | ||||||
| ☒ Cant | ||||||
| ☑ Twist | ||||||
| 10 | PSD | – | ☑ Longitudinal level |
| Depends on data quality & sample representativeness | 2006 |
| ☑ Alignment | ||||||
| ☒ Gauge | ||||||
| ☒ Cant | ||||||
| ☒ Twist | ||||||
| 11 | TQI combined SD (BSI Group, 2010; Tzanakakis, 2013) | Europe standard (EN 13848–5) | ☑ Longitudinal level | Considers four parameters with individual weights | Omits twist – cannot assess derailment risk | 2008 |
| ☑ Alignment | ||||||
| ☑ Gauge | ||||||
| ☑ Cant | ||||||
| ☒ Twist | ||||||
| 12 | IMI (Li & Xu, 2009) | – | Profile, alignment and lateral acceleration, vertical acceleration, history maintenance works | Considers maintenance history, profile, other parameters and penalty factor | Omits gauge & twist – no derailment assessment | 2009 |
| 13 | GEI (Li & Xiao, 2014) | – | Wavelength corresponding to individual irregularity | Considers wavelength effects on train |
| 2014 |
| No | Geometry index | Developer | Parameters | Advantage | Disadvantage | Year |
|---|---|---|---|---|---|---|
| 1 | Standard deviation ( | Europe standard (EN 13848–5) | General method covering various geometry parameters | Cannot measure superposition effect of irregularities | 1981 | |
| 2 | K value ( | Sweden National Railway | Total length of the track with deviations below comfort limits | The irregular length of track can be measured | Does not identify specific irregularities (e.g. longitudinal level, alignment) Ignores location, no maintenance guidance | 2002 |
| 3 | Q ( | Sweden National Railway | Combination of alignment, gauge and cant | Covers cant, gauge, alignment irregularities | Ignores weights of cant, gauge, alignment Omits twist & longitudinal level (vertical irregularities common; twist linked to derailment) | 2002 |
| 4 | Length-based TQI ( | US railway | Traced length of space curve | Measures irregular longitudinal length | Cannot measure lateral irregularities (derailment risk) Lacks location information for maintenance | 2005 |
| 5 | W5 ( | Austrian Railway | ☑ Longitudinal level | Considers correlation among five geometry parameters | Ignores parameter weights | 2000 |
| ☑ Alignment | ||||||
| ☑ Gauge | ||||||
| ☑ Cant | ||||||
| ☑ Twist | ||||||
| 6 | MDZ ( | – | ☑ Longitudinal level | Passenger-centric; focuses on acceleration change over distance | Considers relative error but ignores absolute error Omits gauge & twist; cannot assess derailment risk | 2002 |
| ☑ Alignment | ||||||
| ☒ Gauge | ||||||
| ☑ Cant | ||||||
| ☒ Twist | ||||||
| 7 | American | ☒ Longitudinal level | Comprehensively considers alignment, gauge, cant | Ignores large deviations; no timely alert for dangerous parameters Omits twist and longitudinal level – vertical irregularities common; twist linked to derailment | 2003 | |
| ☑ Alignment | ||||||
| ☑ Gauge | ||||||
| ☑ Cant | ||||||
| ☒ Twist | ||||||
| 8 | TQI ( | Chinese National Railroad | ☑ Longitudinal level | Describes deterioration from statistical & physical perspectives | Ignores wavelength-dependent effects on vehicle (comfort, derailment) | 2003 |
| ☑ Alignment | ||||||
| ☑ Gauge | ||||||
| ☑ Cant | ||||||
| ☑ Twist | ||||||
| 9 | J ( | Polish Railway | ☑ Longitudinal level | Weighted average with lower weight for vertical irregularities | Assumes parameters are independent Omits cant; cannot assess train turbulence | 2005 |
| ☑ Alignment | ||||||
| ☑ Gauge | ||||||
| ☒ Cant | ||||||
| ☑ Twist | ||||||
| 10 | PSD | – | ☑ Longitudinal level | Reflects wavelength effects on track quality Enables comparison of track spectra across countries | Depends on data quality & sample representativeness | 2006 |
| ☑ Alignment | ||||||
| ☒ Gauge | ||||||
| ☒ Cant | ||||||
| ☒ Twist | ||||||
| 11 | TQI combined SD ( | Europe standard (EN 13848–5) | ☑ Longitudinal level | Considers four parameters with individual weights | Omits twist – cannot assess derailment risk | 2008 |
| ☑ Alignment | ||||||
| ☑ Gauge | ||||||
| ☑ Cant | ||||||
| ☒ Twist | ||||||
| 12 | IMI ( | – | Profile, alignment and lateral acceleration, vertical acceleration, history maintenance works | Considers maintenance history, profile, other parameters and penalty factor | Omits gauge & twist – no derailment assessment | 2009 |
| 13 | GEI ( | – | Wavelength corresponding to individual irregularity | Considers wavelength effects on train | Ignores parameter weights and correlations Ignores large deviations; no timely alert for dangerous parameters | 2014 |
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