As locomotivas diesel da série 1520 (1521 a 1525) foram construídas pela American Locomotive Company. Entraram ao serviço em 1952, tendo terminado a sua carreira na CP, tal como as locomotivas da série 1500, a efectuar serviços de passageiros nas linhas do Alentejo e Sul.Ficha técnica da série 1500: Ficha técnica da série 1520:
- 1521 - desmanteladahttp://www.flickr.com/photos/22455491@N02/3884421135/
Comentário do autor: "So far as I can think, the oldest main line Diesel locos in regular service during my Portuguese trips were these 1500 class Alcos. This one appears to be in practically ex works condition as it enters Barreiro station on the south bank of the river Tagus. The station and it's accompanying bus counterpart was a huge transport hub where people continued their onward journey to Lisbon by ferry."
- 1522 - desmantelada
- 1523 - desmanteladaCasa Branca, 11 Novembro 1993
Comentário do autor: "One of the second build of Alco Road Switchers constructed in 1951 for the Portuguese State Railways no.1523 is seen waiting to leave Casa Branca with the 08.20 Barreiro to Beja train. These second series locos were fractionally more powerful than the first batch (CP class 1501) but only five were delivered in 1951. During the 1970 both classes 1501 and 1521 had their original Alco 244 12 cylinder engines replaced by Alco 251-C engines installed at CP's Barreiro works."
- 1524 está no GOBPinhal Novo, 1998
Comentário do autor: "Alco RSC-3 #1524 departs Pinhal Novo on 19/12/98 with IR891 08h25 Barreiro – Beja."
No GOB, 1998
- 1525 foi vendida à Somafel Barreiro, 24 Março 2000
Comentário do autor: "ALCo RSC3 #1525 at Setubal with R3801 16h35 Barreiro to Funcheira on 24/03/00"