Availability differs from reliability

From Malcolm Watson, Ryde:

I READ our MP Bob Seely’s vision on ferries (CP, 18-06-21) with great interest, but he mixes up reliability with availability.

It is availability that “has been above 95 per cent” not reliability.

It is important to understand the difference.

Availability, also known as operational availability, is expressed as the percentage of time that a ferry is operating compared to its total scheduled operating time.

Reliability is expressed as the duration of operation without failure and will influence the number of ferries, spares and the repair policy required to meet a given availability.

It is availability that customer expectations are built upon; reliability is the concern of the operators.

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