CP Class 1800

The Série 1800 were a series of 10 diesel-electric locomotives built for the Portuguese Railways (CP) in 1968. Designed and engineered by English Electric, they were closely modelled on the British Rail Class 50 locomotives but built for CP's 5' 6" (1668mm) track gauge and larger loading gauge than possible in Great Britain.

Like the British Rail Class 50s, they were equipped with an English Electric 16 CSVT engine and produced 2700 hp. Unlike the Class 50 locomotives, which made extensive use of electronic control, the Portuguese locomotives were equipped with conventional control gear. The main generator and the traction motors were identical to those used on the BR Type 3 and Deltic locomotives. The Série 1800 locomotives were built to be closely compatible with the smaller CP Série 1400 (themselves based on the British Rail Class 20) and also to use as many common components as possible. They were the only diesel locomotives in Portugal authorised to run at 140 km/h (87 mph).

The Série 1800 were all withdrawn in 2001, apart from one withdrawn earlier due to an accident. Initially they were used on the express services between Barreiro (near Lisbon) and Faro, later being relegated to Inter Regional services in the Algarve. The main line between Lisbon and Faro is now electrified.