The Class 37 is a 1,750 hp Co-Co diesel-electric locomotive introduced by British Rail between 1960 and 1965, with 309 locomotives built. Designed for versatile mixed-traffic duties, it became one of Britain’s most successful and recognisable diesel locomotive classes.

Known affectionately as the “Growler” or “Tractor” because of its distinctive engine sound, the Class 37 has worked passenger, freight and specialist services across the UK. Despite being more than 60 years old, a number of Class 37 locos remain in mainline service today, including with Rail Operations Group.

With more than 60 years of history, the Class 37 continues to prove its reliability, versatility and enduring performance, making it a locomotive trusted by rail professionals across the UK.

Below are the benefits of Class 37:

• Highly reliable – a proven design with decades of operational experience.
• Versatile – suitable for both passenger and freight duties, as well as specialist train movements.
• Robust and durable – built to withstand demanding railway operations.
• Easy to maintain – its established design and widespread use mean good availability of knowledge and parts.
• Proven performance – capable of hauling a wide range of rolling stock across the UK network.
• Long service life – many locomotives have remained in use for more than 60 years.
• Distinctive and recognisable – the Class 37 is well known for its characteristic engine sound and strong presence on the railway.