We thank Mr Chan Yeow Chuan (Biased figures on MRT breakdown rate; July 29) and Mr Tan Shao Yi (Use more meaningful measures in evaluating the MRT; July 31) for their letters on measuring our rail reliability.
Improving rail reliability is a multi-year effort. The purpose of the mean kilometres between failure (MKBF) for delays of more than five minutes indicator is to track our progress from year to year, and to provide an objective benchmark for comparison with other metros.
We benchmark ourselves against both Hong Kong and Taipei, as these two cities boast metros which are objectively best-in-class for reliability, and for which some data is available.
Besides the MKBF, we also track the absolute number of delays of more than 30 minutes. Reporting on these longer delays in absolute terms is more intuitive for the public, given also their relatively smaller numbers.
Re-signalling on the North-South and East-West lines takes place once every 30 years or so. Even though we have tried to minimise it, delays during the testing phase will invariably occur.
Including such delays in the MKBF will not give an accurate nor fair picture of the underlying rail reliability or railway maintenance performance.
We ask for commuters' patience. Once the new signalling system stabilises, commuters on the North-South and East-West lines will enjoy a more reliable train system and more frequent trains.
Ngien Hoon Ping
Land Transport Authority