The refurbishment is designed to extend the life of the trains by another 20 years. The work involves fitting new interiors, doors, and air-conditioning equipment, installing a new communications system, replacement of the traction equipment, and supply of static converters for auxiliary equipment. Alstom says the modernised trains will use 30% less energy than now.

The work, which is due to be completed in mid-2018, will be carried out at Neptuno depot to minimise disruption to train operations on lines 2 and 5. Alstom will also provide technical assistance and be responsible for maintenance of materials for 10 years.