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The reliability benefits are calculated by the Reliability Model in the Business Case Model. The model makes assumptions about how DTO and UTO would impact the Reliability and Regularity performance measures, and then estimates how these two measures combined relate to passenger journey times.
Regularity Reliability CSS 2005 88.75 95.95 2006 88.75 95.95 2007 91.66 96.39 7.755 2008 94.32 96.88 7.8 2009 95.67 96.91 7.835 2010 94.55 96.25 7.69
Table 32 Historic Regularity, Reliability & Customer Satisfaction Scores CSS v Reliability CSS v Regularity Reliability v Regularity
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The above data suggests that of the two train service measures, Reliability is the probably the most important. Improvements to either ought to improve journey times and customer satisfaction but to add-together the results of Reliability and Regularity would double-count their effect on journey times. However, to use just the Reliability measure would under-estimate the effect. Therefore the two measures have been combined to a produce a “Combined Performance” based on the above relationship. The table below contains the predicted differences in performance between STO, DTO and UTO. The STO base case statistics are taken from 01/01/2010 – 07/06/2010. The “Combined Performance” is thus calculated for STO, DTO and UTO.
Reliability = 1 - Share Cancelled
Regularity = 1 - Share Delayed Rel i a bi l i ty Regul a ri ty Rel i a bi l i ty Regul a ri ty Rel i a bi l i ty Regul a ri ty 0.01 0.03 0.01 0.03 0 0 0.01 0.07 0.01 0.07 0 0 0.02 0.00 0.02 0.00 0 0 0.01 0.07 0.01 0.07 0 0 0.00 0.00 0.00 0.00 0 0 0.09 0.01 0.09 0.01 0 0 0.00 0.00 0.00 0.00 0 0 0.00 0.01 0.00 0.01 0 0 0.00 0.00 0.00 0.00 0 0 0.01 0.01 0.01 0.01 0 0 0.00 0.00 0.00 0.00 0 0 0.00 0.01 0.00 0.01 0 0 0.00 0.02 0.00 0.02 0 0 0.00 0.01 0.00 0.01 0 0 0.64 0.91 0.64 0.91 0.32 0.46 0.04 0.11 0.03 0.07 0.03 0.09 0.09 0.07 0.06 0.05 0.06 0.05 0.06 0.03 0.02 0.01 0.01 0.00 2.86 4.59 2.86 4.59 2.29 3.67
TOTAL RELIABILITY & REGULARITY 3.85 5.98 3.61 5.64 2.71 4.27
TOTAL COMBINED "PERFORMANCE" 4.57 4.29 3.22
Train Driver Feed
Coverage ratio
Failure to break
Replac ed the late Illness
Train Operator Error
Prac tice Signal passing Viewed wrong turn
STO DTO UTO
Appeared too late Taxa Compared Toilet visit
Stood on Wrong platform Recovery after Disorder
Equipment (4) gene c ompared Vandalism
Trac kside Sec urity Person Colliding Near c ollision Impact & rec overy from other incidents
Table 33 Prediction of Reliability and Regularity under DTO and UTO
The important assumptions are:
i) Under UTO problems caused by train drivers are eliminated.
ii) Under UTO train equipment is 50% more reliable due to the improved specification assumed for a new “UTO capable” fleet.
iii) Under DTO, and to a lesser extent UTO, there is less vandalism due to higher staff presence (33% and 16.7% respectively).
iv) Under DTO and UTO there are less collision and “near miss” delays due to the increased track-side security.
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v) Under UTO it is easier to recover from all incidents due to the ability to more easily divert and reform train trips to return more quickly to the plan (20% better recovery).
These calculations produce a “Combined Performance” result for STO, DTO and UTO. These results are converted into travel time benefits per passenger. The assumed relationship is that for each point improvement in the “Combined Performance”, the travel time improves by 0.63% (based on a nominal 20 minute journey). This assumed relationship is explained in more detail below.
A lost (percentage) point in the “Combined Performance” measure corresponds to 1% of “missed headways”. Therefore 1% of passengers have an extended wait time. If the “missed headway” is the result of a delay rather than a cancellation, a further 1% of passengers experience the equivalent delay in their time on the train. Assuming on average, passengers usually experience a 5 minute headway (and therefore a 5 minute weighted wait time) and a 15 minute running time, then, if half of the missed headways arise from delays then the journey time increases from 20 mins to (20.10+20.15)/2 = 20.125 mins (i.e. a 0.63% increase).
50% Simple Cancellation 99% Achieved Headway 1% Mis sed Headway Average Wait Time 5 15 Train Time 15 15 Total Time 20 30 20.10 % Affected 99% 1%
50% Cancella tion as result of Delay
99% Achieved Headway
1% Missed
Hea dwa y Avera ge
Wa it Time 5 15
Tra in Time 15 20
Total Time 20 35 20.15
% Affected 99% 1%
Table 34 Relating Reliability & Regularity to Journey Time
The Business Case Model can calculate the annual travel time saved for each option due to an improvement in the “Combined Performance”. An option may have different modes of operation on different parts of the network, so the “Combined Performance” improvements will only apply in proportion to the number of trains operating in each mode.
STO DTO UTO
Reliability 96.15% 96.23% 97.29% See above
Regularity 94.02% 94.10% 95.73% See above
Combined Performance 4.57 4.48 3.22 100*{(1-Rel) + [0.12 x (1-Reg)]}
% Travel Time Lost 2.86% 2.80% 2.01% Combined x 0.63% Table 35 Journey Time Improvements due to Reliability and Regularity
The Business Case Model will, in each year, compare the selected option defined to be in operation for that year of the programme with the option that is assumed in that year of the base case programme. The difference in journey times will be converted into a socio-economic benefit for that year of the programme.
The methodology described in this section 7.3 is certainly not perfect. The existing Reliability and Regularity measures are both based on meeting a timetable objective (punctuality and numbers of departures as specified in the timetable) rather than a headway or journey time measure. Also the statistical relationships between the measures are not strong. There appears little research to draw upon. Parsons, have spent some time analysing the available performance data in a number of different
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ways, and had various discussions with DSB and Banedanmark performance analysts. However Parsons have been unable to find a way to improve this described methodology within the timescales of this study (to do so would probably require some complex disruption modelling). However, the results of this simple analysis (around a 1% journey time reduction for UTO v STO) seem reasonable compared to results from the modelling of UTO benefits previously performed for London Underground and are therefore considered suitable for use in this study.