Soaring temperatures have scorched the ScotRail Alliance’s punctuality to its worst June/July figure for 17 years.
The heatwave caused widespread disruption to tracks run by alliance partners Network Rail, which contributed to nearly one in seven trains arriving late.
Punctuality in the four weeks to 21 July was 85.5 per cent.
That compares to 93.7 per cent a year ago and the lowest for that period since 2001.
The figure shows the proportion of trains reaching their destination within five minutes of schedule.
The latest dip means the alliance’s underlying punctuality has now fallen for nearly a year, to 88.4 per cent.
That figure is now worse than when the first of two performance improvement plans were introduced in 2016.
However, there was also better news for ScotRail with a significant fall in fines for failing to meet service quality standards.
The alliance admitted it had faced a “challenging” period, when rail temperatures reached 50C, forcing speed restrictions that disrupted trains across the Central Belt.
There were also a series of signalling faults, mainly around Glasgow.
Managing director Alex Hynes said: “I’m sorry to our customers who have experienced disruption recently due to the problems with track and signals. This, combined with the extremely hot rail temperatures, meant our performance has simply not been good enough.
“Customers expect a reliable service and my teams in Network Rail Scotland and ScotRail are determined to give them that.”
Mr Hynes said an extra £5 million to improve track and signalling reliability would be spent over the next months.
Transport secretary Michael Matheson said: “I’m acutely aware of the challenges and factors affecting rail performance historically and more recently.
“This public acknowledgement, by senior management, is a clear indication of the impact on passengers and I expect the ScotRail Alliance to work closely together to build on the lessons learned to date.”
Meanwhile, ScotRail penalties under the Service Quality Incentive Regime - Britain’s toughest - fell from £448,820 in April to £351,308 in June.
The three-month total of nearly £1.2 million was also well down on fines of almost £1.6m from January to March.
However, facilities such as train and station toilets, passenger information and seat reservations remained below par.