Not since before Abellio took over the ScotRail franchise in 2015 has the July-August public performance measure (PPM) been so low.

PPM is the rail industry standard based on how many trains arrive at their destination within 4 minutes and 59 seconds of their timetabled arrival.

Across the country, 88 per cent of ScotRail trains met the PPM between July 21 and August 17. This marks the worst punctuality figures for the transport operator since December.

Scotrail said it is committed to keeping Scotland moving.

The rail industry compares PPM in blocks of time against previous years to take into account seasonal weather change.

But this summer Scotland has been hit by both extreme heat and heavy rain.

The four-week window included flooding at Winchburgh Tunnel which closed the main Edinburgh to Glasgow line causing a 1.6 er cent PPM reduction. More than 60 percent of the average August rainfall fell in just three hours and emergency crews were called in to reduce water levels.

The severe rain hit the West Highland Line with thousands of tonnes of material falling away from beneath tracks. Torrential rain also caused several landslips.

Affected passengers were provided with replacement buses.

Alex Hynes, Managing Director of Scotland’s Railway, said: “This latest period of performance brought considerable challenges to every aspect of Scotland’s Railway and I am proud of everyone for their dedication and commitment, working round-the-clock, to keep our customers moving.

“I understand and share the frustrations of our customers when things go wrong, but thanks to the ever-improving measures we are establishing to tackle incidents of this nature, I am pleased with how quickly we were able to restore services.

“The unprecedented investment in upgrading the infrastructure, and introducing new and upgraded trains, is delivering a consistent level of performance and I am looking forward to continuing improvements in the weeks and months ahead.”

Abellio is investing £475 million in new and upgraded trains.

ScotRail highlighted that the July-August figures show the best period for train crew related cancellations since the Christmas timetable change.

ScotRail summer punctuality at lowest level since before Abellio takeover