A total of 20 units, service numbers AES1 - AES20, have been built in Argentina by the English company GEC and Argentine company Fiat Concorde (FIAT MATERFER) between 1976 and 1977. Their main area of passenger service has been rapid suburban transit between Valparaiso and Limache, with extended service between Valparaiso and Santiago during the 1980s, and service on the Biotren in the South of Chile since the 2000s. Their maximum speed is 130 km/h (80 mph).
There was a major accident at the town of Queronque on February 17, 1986, involving two AES units. It was the largest railroad accident in the history of Chile.
Another three AES units were set on fire by terrorists.
In the early 2000s, MERVAL has gradually introduced new UT440R (Unidad de Tren 440 Reformado) railcars,
bought second-hand from Spain and refurbished. After operating side-by-side with the AES units for a brief period, they have completely taken over passenger service on June 30, 2005. On that day, AES 17 and AES 3 operated the last MERVAL revenue service between Puerto and Limache, in a large public event that included live music and celebrities.
Although the change to the sophisticated, quieter, airconditioned and technologically advanced Alstom X'trapolis units has been met with a very positive public response, there are many Chileans who feel nostalgic about the AES trains that have been part of their daily lives for decades, in the future model AES train, used service especial tourist "Train Memory".
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