Heavily disrupted rail services from Cumbernauld and Greenfaulds to Glasgow Queen Street will not be fully restored until March next year.
Since June, buses have been brought into replace rail services on a Sunday and selected services after 8pm.
The reduced services are the result of engineering works by Network Rail to electrify the lines. This is in a bid to improve rail provision.
However, Sunday services have finally returned to normal in the run-up to the festive season.
Trains went back on track at the weekend,in a boon for Christmas shoppers.
Howevever, this will be for a temporary period only as the giant engineering project still has some way to go before its completion.
A spokesperson for Scotrail confirmed: “We have returned to a normal service until Sunday, December 29.
However, disruption will continue to affect some evening services until after 8pm. Any services disrupted by engineering works will be replaced by buses.
Passengers should check our website for the latest information.
“Engineering works will resume again on January 5 until March when Network Rail’s works are scheduled to be complete.We will operate buses to keep disruption to a minumum for passengers,’’ she added.
Andrew Stephen of the Cumbernauld Commuters Association said that the disruption would ultimately pay off and could have been more widespread in the circumstances.’’
He said: “Peak hour commuter services are not affected by the altered timetables. The disruption to weekday evening and all Sunday services is a small price to pay for the long-sought electrification, upgrading and development of the Cumbernauld line.’’