Investigation of the effect of the inspection intervals on the track geometry condition

Figures & data

Figure 1. Different maintenance zones based on limits.

Figure 2. Examples of UH1, UH2 and critical defects of the longitudinal level.

Table 1. Maintenance limits defined in the European standard EN 13848-5 and in Trafikverket (2015).

European standard EN 13848-5	Trafikverket (2015)
Alert limit	Planning limit
Intervention limit	UH1 limit (lower bound for corrective maintenance)
	UH2 limit (upper bound for corrective maintenance)
Immediate action limit	Critical limit

Figure 3. Schematic description of preventive and corrective maintenance actions.

Table 2. Three defined track geometry states based on the maintenance limits.

State	Definition
1	There is no UH2 defect or critical defect in the track section.
2	There is at least one UH2 defect in the track section, but there is no critical defect in that section.
3	There is at least one critical defect in the track section.

Figure 4. Histograms of the initial degradation value and degradation rate.

Table 3. The results of parameter estimation for lognormal distributions.

	Location parameters	Scale parameter
Initial degradation value	−0.17	0.26
Degradation rate	−2.77	0.61

Table 4. Parameter estimates for recovery model.

Parameter	$a_1$	$b_0$	$b_1$	$b_2$	$b_3$	$b_4$	$b_5$	${\mathrm{\tau }}^2$
Estimates	1.08	0.32	0.36	−0.13	−0.23	−0.30	−0.36	0.06

Figure 5. (a) Box plot of the recovery values for different numbers of tamping interventions, (b) Box plot of the recovery values for different tamping types.

Table 5. The ordinal logistic regression results for the longitudinal level defects.

	${\theta }_1$	${\theta }_2$	SDLL
P-value	<0.05	<0.05	<0.05
Coefficient$$	9.8	13.02	−5.02

Figure 6. Relationship between the standard deviation of the longitudinal level and the probability of no defect, at least one UH2 defect, and at least one critical defect in a track section.

Table 6. Effect of the inspection interval on the percentage of time spent in the different longitudinal level states.

Inspection interval	State 1	State 2	State 3
1 Month	99.26%	0.69%	0.05%
2 Months	98.55%	1.35%	0.10%
3 Months	97.85%	2.01%	0.14%
4 Months	97.20%	2.62%	0.18%
6 Months	95.79%	3.91%	0.30%

Trafikverket. (2015). Banöverbyggnad – Spårläge – Krav vid Byggande och Underhåll (Track superstructure – Track geometry – Requirements after renewal and maintenance, in Swedish). TDOK 2013:0347 v3.0. Borlänge, Sweden: Trafikverket.

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