IT is the end of the line for the controversial practice of flushing raw sewage onto railway tracks as the first of 47 trains due to be fitted with non-discharging toilets prepares to join the ScotRail fleet.

Work on the first of 47 Class 156 ScotRail trains installed with Control Emission Toilet (CET) equipment is due to be completed on Friday, with the unit scheduled to be moved back into circulation over the weekend.

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It marks the beginning of the end for the practice of dumping human waste onto Scotland’s rail lines.

An additional nine units are due to be fitted with CET equipment before Christmas as part of a £382,000 package of works funded by Transport Scotland.

By the end of 2017, all ScotRail trains will be fitted with CET equipment which means that the effluent is held within a hygienic tank on the train until it is emptied at an appropriate location, usually at depots or stations.

The commitment puts Scotland ahead of rail networks around the rest of the UK where the practice still continues.

Members of the National Union of Rail, Maritime and Transport Workers (RMT) threatened industrial action last year following complaints that railway maintenance staff were having to endure unpleasant discharges from on-board toilets as they worked on tracks.

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Transport Minister Derek Mackay said: “The discharge of effluent onto the tracks is unpleasant for both staff and passengers and from day one it has been a priority of mine to end this practice in Scotland.

“I am pleased that the Scottish Government has been able to work together with ScotRail to accelerate the initial timeframe for this, and we are investigating further measures to bring forward the completion date.

“This is a great example of ScotRail working with industry partners to deliver a project which benefit passengers and rail workers, and I am committed to ongoing discussions with the UK Government to also end this practice on cross-border operators.”

RMT has previously urged the Scottish Government to bring forward the deadline to April 2016.

Around 90 per cent of ScotRail carriages with toilet facilities already have effluent retention tanks but the C156s, built in 1988, do not.

Work on the C156 units is being carried out at the Knorr Bremse Rail Services plant in Springburn, Glasgow.