Zbornik radova Koridor 10 - Kirilo Savić

3rd International Scientific and Professional Conference
CORRIDOR 10 - a sustainable way of integrations
Three main geometric quality levels are defined in the European Standard EN 13848-5 [5].
The first level is Immediate Action Limit (IAL). It refers to the value which, if exceeded, requires taking
measures to reduce the risk of derailment to an acceptable level. This can be done either by closing
the line, reducing speed or by correction of track geometry.
The second level is Intervention Limit (IL). It refers to the value which, if exceeded, requires corrective
maintenance in order that the immediate action limit shall not be reached before the next inspection.
The third level is Alert Limit (AL). It refers to the value which, if exceeded, requires that the track
geometry condition is analyzed and considered in the regularly planned maintenance operations.
Table 1 gives the overview of the main geometric quality levels of the track geometry parameters.
Tab.1. Quality levels of the track geometry parameters according to EN 13848-5 [9]
Nominal to peak Nominal to mean
Zero* to peak value Standard deviation
value
value
IAL IL AL IAL IL AL IAL IL AL IAL IL AL
Track gauge + + + + + +
Longitudinal
level
+ + + +
Alignment + + + +
Twist + + +
* According to [5], mean to peak values are defined for longitudinal level and alignment. In practice the
mean will be close to zero and therefore zero to peak values may be used.
The immediate action limit values are derived from experience and from theoretical considerations of
the wheel-rail interaction.
For the track gauge, the standard provides limit values for isolated defects (minimum and maximum
nominal track gauge to peak value) and for mean track gauge (nominal track gauge to mean track
gauge over 100 m section).
For the longitudinal level and alignment mean to peak values are defined. The mean values are
calculated over a length of at least twice the higher wavelength in the D1 range: 3 m < λ ≤ 25 m or D2
range: 25 m < λ ≤ 70 m.
The immediate action limit for the track twist as the isolated defect is given as zero to peak value.
The standard gives no immediate action limit values for cross level because the risk of derailment
associated with a cross level defect is tied to twist and cant deficiency. Cant deficiency limits depend
on the track alignment design and construction rules, and the characteristics of the traffic, on each
network.
The immediate action limit for the track gauge is given as a function of maximum speed of vehicles
running on the line, while the immediate action limits for the longitudinal level and alignment are given
also as a function of wavelengths D1 and D2. The wavelength range D3: 70 m < λ ≤ 200 m (generally
this range should only be considered for line speeds greater than 250 km/h) is not taken into account,
as it is not directly linked with safety, but more with vehicle ride quality. The immediate action limit for
the twist is a function of the measurement base-length applied.
The intervention and alert limits are mainly linked with maintenance policy. Maintenance policy may be
directed either at upholding safety alone or at achieving good ride quality, lower life cycle costs or
more attractive (higher speed) services in addition to safety. The alert limits and intervention limits set
by the European infrastructure managers will be set at least to ensure safety and can be tightened to
achieve a given level of ride quality [5].
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