Reliability of Stockholm Subway - Index of

terminal and departure time at the starting station. Big variability of the parameter can
reveal problems with the network and signaling system.
To estimate actual travel times statistical measures such as mean and 85% percentile
are usually applied by operators.
The inconsistency of actual travel times to
scheduled ones may be a ground for timetable reconsideration and improvement.
3.1.5 Headway adherence
Headway adherence (or in other words deviation of headway) described in TCQSM
can characterize service punctuality for the transit service operating at headways of 10
minutes or less. “The measure is based on the coefficient of variation of headways of
transit vehicles serving a particular route arriving at a stop” (TCQSM). It is calculated
as a difference between actual and scheduled headways at a studying time point.
Coefficient of variation (CVH) of these differences informs about the level of service
at the studying time point.
(3.1)
where the headway deviation is the difference between the actual headway and the
scheduled one. Level of service classification is presented in table 3.1.
Table 3.1 Level of service according to TCQSM
LOS CVH P (hi > 0.5 h) Comments
A 0.00-0.21 ≤1% Service provided like clockwork
B 0.22-0.30 ≤10% Vehicles slightly off headway
C 0.31-0.39 ≤20% Vehicles often off headway
D 0.40-0.52 ≤33% Irregular headways, with some bunching
E 0.53-0.74 ≤50% Frequent bunching
F ≥0.75 >50% Most vehicles bunched
NOTE: Applies to routes with headways of 10 minutes or less.
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