On page 144 of his book, Wardale makes the point that improving reliability could fall into the category of improving Performance and Efficiency in the broader meanings of the words. For instance:
- any enhancement that improves steaming will improve a locomotive's operational reliability;
- any enhancement that improves performance will give a locomotive a margine for time recovery and thereby improve reliability of on-time arrival;
- any enhancement that reduces maintenance will improve a locomotive's reliability in terms of its availability for work.
To that extent, every modernisation option listed in these pages will serve to improve reliability in one form or other. It is for this reason that ticks have been applied to all the boxes tabulated in the Options page.
In the more limited sense of improving reliability by reducing incidents of breakdown, selection of one option over another is rather more difficult since any machine that is designed, built, maintained, serviced and operated properly should seldom suffer failures. Indeed, consideration should be given to implementing a preventative maintenance system "with inspections of wearing parts at stipulated intervals, dictated by rates of wear of individual components and systematic replacement of worn parts, determined by gauges set to limits of wear".
Note: the quoted words above come from Porta's 1969 Manchester Paper (as published in Advanced Steam Locomotive Development) and describe the preventative maintenance system adopted by SNCF in France "which enabled its steam locomotive fleet to maintain an average mileage of 156,000 between on-line failures".]
Wardale raises the important point that considerations of the reliability of steam traction extends beyond the locomotives themselves but should take into account reliability of coal quality and of water treatment.
He goes on to suggest that if overall reliability is improved through the implementation of Porta's moderisation principles to the extent that locomotives (in both heritage or main line service) are always available when they should be and do not cause problems, all this with the minimum of maintenance attention, it will be of greater practical benefit to operators and will be appreciated much more than any improved performance or reductions in coal or water useage.
Emphasising this point, Wardale recommends that any modernisation effort should concentrate on three things: to paraphrase a political slogan -
Reliability, Reliability, and Reliability.