VIRM trains, full name Verlengd InterRegio Materieel (Lengthened interregional rolling stock), are a series of electric multiple unit (EMU) double-deck trains operated by Nederlandse Spoorwegen or NS (Dutch Railways), the principal railway operator in the Netherlands. NS has 178 of these double-deckers – 98 four-carriage sets, and 80 six-carriage sets. The trains were built between 1994 and 2009 – for the most part by Talbot, part of Bombardier Inc., with some railcars built by De Dietrich. The VIRM trains evolved out of the previously existing DD-IRM series (DubbelDeks InterRegio Materieel or Double-deck interregional rolling stock). The first batch of 81 VIRM trains was created by lengthening all the existing DD-IRM combinations by one or two railcars. Three-unit trainsets were augmented by one carriage to transform them into a four-unit VIRM, and the four-unit sets received two more carriages, to create six-unit VIRM trains.