The MRT system’s unreliability continues to be a bane, with the latest two incidents happening last week (Train delay on North-South Line, second disruption in a week; Aug 31, online).
This does not square with the recent announcement that rail reliability has improved (Khaw raises bar for rail reliability, sets new target; July 28).
This reliability, measured in mean kilometres between failure (MKBF), has not translated into an improved commuter experience.
Knowing that trains will be punctual according to a timetable would be more useful for commuters and would promote greater accountability on the part of the operator (Put up daily train timetables at all stations; Aug 2).
Reliability, based on punctuality, can be measured using a train-to-station metric, which is the product of the number of trains and the number of stations along their journey.
For instance, a train making a 20-station journey would achieve a punctuality of 95 per cent if it was delayed at only one station. Overall MRT reliability can be calculated on all the journeys made by trains.
With zero and 100 as the lower and upper bounds, this measurement of reliability should match the commuter’s experience more closely.
This metric also captures the relative impact of each delay. A short delay would result in a small loss of train-to-station units, while major incidents would cause a substantial loss, since many arrivals would be affected.
In contrast, MKBF does not adequately capture the length of delays, particularly those that cause the most havoc.
So commuters can plan their journey better, another suggestion is to provide the arrival times of the next three to five trains, and to indicate whether each will be punctual or delayed, instead of the number of minutes until the next train arrives.
Finally, failure should be defined more stringently than as a delay exceeding five minutes. It should be two minutes at most.
With peak train frequencies of two to three minutes, a five-minute delay would cause two or three subsequent trains to be delayed in arriving at a specific station.