Calcutta Metro will start 'maintenance runs' of trains from Thursday to check the condition of the fleet, grounded since March 25. 'The trains will run between the terminal stations of Dum Dum and Kavi Subhash (New Garia). Metro maintenance staff will be on the trains to check the fitness of the rolling stock and other assets. All the rakes will be tested in turns. The signalling system will also be checked,' a Metro spokesperson said.