 The subsequent investigation found that a wiring error during a modification to the train's low-note whistle on 959M, combined with a deterioration of insulation resistance in the uncouple solenoid connector of 882M (the leading car of the trailing unit), resulted in an error circuit forming which resulted in the unintended coupling.Valparaíso has had an interurban passenger train system since the 19th century, but it could not be called a metro due to an infrequent train service and other shortcomings.In 1999 construction began on the current system, tearing down the old stations and building new ones with a homologous design.