Train passengers using Cumbernauld and Greenfaulds stations now face a partial rail replacement service on some weeknight journeys.
Key engineering works have now begun between these two transport hubs and Springburn.
This is where services to Balloch will terminate to allow a multi-million pound refurbishment of Greenhill and Cumbernauld
This stretch of the line will be closing from 8pm from Mondays to Thursdays until mid October.
However, trains on the original Falkirk Grahamston to Glasgow route will not be affected by the work.
Network Rail insists that the work must be done at this stage to avoid problems at a later date.
A spokesman said: “The Greenhill Junction is a vital piece of infrastructure which links trains into the Edinburgh Glasgow Cumbernauld Line and the line north of Stirling.
“It is vital we replace this track through this area and other associated equipment as the current infrastructure is reaching the end of its life span. It’s a complex and extensive piece of work and cannot be delivered without some short-term service disruption but engineers will be working hard to complete the works as quickly as possible.’’
We’ve reported how these stations have the least reliable routes in Scotland following the publication of a document last month by train operators themselves.
Cumbernauld was the target of a multi-million pound revamp which brought more trains to the town but the statistics showed that there has in fact been a reduction in service.