The series 4000 designates ten tilting high speed trains built for the “Alfa” services between Lisbon and Porto. They have been designed by FIAT and built in 1999 and 2000 by Sorefame in Amadora. They were based on the Italian ETR 460, but only have six cars per set. Although they were designed for 220 km/h, they could only be operated at 160 km/h until the line between Lisbon and Porto had been upgraded. The services were later expanded from Lisbon to Faro and from Porto to Braga. 