The firm that looks after railway tracks and signals said heat-related problems in the Midlands are not as bad as passengers may think.
It comes after problems on Birmingham and Wolverhampton services heading into Shropshire, and for other trains passing through Warwickshire this week.
A hot weekend has raised fears of more tracks being affected by the heat.
But Network Rail's Ben Herbert said ongoing work means the bulk of trains in the region continue to run on time.
He said: "I think it is sometimes the case that people can get a bit carried away thinking the weather is causing havoc with the railways. It is not.
"Nine out of ten trains are running on time and we do a lot of work in terms of how we renew the railways to ensure it can cope with all kinds of weather."
Stuck on trains
The warm weather was blamed for problems with signals and tracks across the Midlands in the past few days with some trains having to slow down.
A temporary 5mph limit was brought in at Rugby.
And thousands of passengers were stuck on crowded trains between Shropshire and Birmingham on Thursday due to a series of problems with signals and the track.
These were compounded by an emergency line closure in Wales causing problems with long-distance trains running to Shropshire and Birmingham.