RAIL commuters will test contingency plans for the closure of Glasgow's Queen Street tunnel this morning in the first rush hour period following the start of a major renovation.

The station's high-level tunnel - which is used by the Edinburgh, Aberdeen and Stirling services - closed on Sunday for five months to allow complex engineering work to take place.

Diversions caused by the work mean that most journeys will take around 25 minutes longer than usual as trains are directed to a lower tunnel or Glasgow Central.

Passengers are being urged to plan their trips in advance and arrive at the station 10 minutes earlier to allow for the changes, which will see people escorted to trains from marquees positioned outside the station building.

Queues are also expected at other major stations, such as Glasgow Central and Edinburgh Waverley during busy periods.

Robert Samson, passenger manager for Transport Focus, said: "If the rail industry is to retain the confidence and trust of its passengers, it is vital ScotRail takes full account of their needs during the disruption.

"Our research tells us passengers want to be told clearly, early and often how engineering work will affect them.

"ScotRail has been keeping passengers informed through its website and social media, leaflets at stations and announcements on trains. We are pleased to see this proactive approach."

The 20-week upgrade of the Queen Street tunnel, estimated to cost £60 million, is being carried out to allow faster, longer and greener trains to run between Edinburgh and Glasgow and to replace ageing track through the kilometre-long structure.

Tracks which are more than 40 years old will be replaced and power lines installed to allow electric trains to operate on the route from December 2016.

Work inside the tunnel began on Sunday morning once it was closed.

Transport minister Derek Mackay inspected plans for the closure on Friday.

He said: ''They are absolutely necessary works. Of course there's the inevitable disruption we are trying to minimise. This is why we have put so many contingency plans in place.

''It's the tracks that are being upgraded and repaired, upgraded not for a few years but for a generation."

He added: "The closure of the Queen Street station high-level tunnel marks a further significant milestone in our £5 billion programme of investment in Scotland's railways and will pave the way for the introduction of a new generation of electric trains for the central belt of Scotland."

Train passengers are urged to visit the ScotRail website to familiarise themselves with the temporary layout of the station, and with the temporary timetables.

Officials warn that a number of services to and from places around Scotland will be affected by the work, not just services local to Glasgow.

John McBrinn, senior customer manager with the ScotRail Alliance, said their key message is for passengers to plan ahead and allow more time for their journey.

"All the information that people need is available on our website," he said. "We will have extra staff in the stations to answer questions and help get you to the train."