sentences:  In the summer of 2016, guards working for Southern and belonging to the RMT trade union went on strike over plans to introduce DOO on more Southern services.DCO was first implemented in the 1980's and currently more than 56% of ScotRail's trains are one-man operated, mainly electric services around the Glasgow and Strathclyde regions.When First ScotRail launched a plan to implement one-man operations on the newly opened Airdrie-Bathgate Rail Link in 2010, the National Union of Rail, Maritime and Transport Workers (RMT) staged several strikes, claiming that the system was unsafe.