V/Line's monthly performance figures show 91.9 per cent of Warrnambool line services arrived on time in August.

That result is up more than three per cent from the month before and also marks an improvement on the same time in 2018 when 90.7 per cent was recorded.

But, it was just shy of V/Line's punctuality target of 92 per cent, which has been hit just 12 times in 10 years, and only once in 2019.

In June, 92.5 per cent of services arrived on time.

A V/Line spokesman said service reliability remained strong with 97.4 per cent of trains running in August, making it the sixth month in a row that less than 10 scheduled services were unable to run.

"While this result is encouraging, we are continuing to work on ways to improve performance on Warrnambool trains, particularly on the parts of the line they share with other V/Line services," he said.

Of the 224 services that operated during August, 204 arrived within the nominated threshold of 10 minutes and 59 seconds.

Services were delayed or replaced by coaches for a mix of reasons in August, including an emergency services incident near Warrnambool and trains stopping at platforms for longer than usual at stations closer to Melbourne.

V/Line has been trialing a number of initiatives to improve performance on south-west services, including an increased staff presence to help reduce boarding times at inner-city stations.

Coaches will replace Warrnambool trains for six days at the end of the month as construction continues on the Metro Tunnel's western entrance in Melbourne.

The works will interfere with the dedicated tracks that carry V/Line trains to and from Melbourne.

V/Line maintenance work will also see coaches replacing trains on the Warrnambool line in late October.

Transport Infrastructure Minister Jacinta Allan apologised for the disruption.

"But we can't deliver the biggest upgrade our train network has ever seen without them," she said.

"These works pave the way for more services, bigger trains and less congestion on our busiest roads."

Temporary timetables will be available closer to the date.

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