The Rail Accident Investigation Branch (RAIB) has set out the investigation it will be carrying out into the derailment of a Metrolink tram in Manchester last month.

The incident, in which no-one was injured, took place on Sunday 5 April at about 13:39 (1:39pm). A tram which was travelling from Ashton to Bury derailed as it was approaching Piccadilly tram stop in Manchester.

The tram was travelling at about 8 mph (13 km/h) when the wheels on one of its axles left the track. The tram was formed of two coupled sets. The driver was not aware of the derailment at the point that it happened, and the tram continued into the tram stop, where passengers disembarked.

The tram and the infrastructure sustained minor damage only.

The RAIB revealed that its investigation will examine the sequence of events leading to the derailment, and that it will consider factors such as:

• the design of the track at the location of the derailment, together with the way in which it was maintained and managed
• similarly, the design of the tram that derail, together with the way in which it was maintained and managed
• how the tram was operating at the time that it derailed
• any underlying factors which might have contributed to the tram derailing.

The Rail Accident Investigation Branch stresses that its investigation is independent of any investigation that may be carried out by the tramway industry or by the Office of Rail and Road (ORR). The role of the RAIB is to carry out such independent investigations in order to identify the causes of railway (including tram) accidents and identify measures to reduce the risk of a recurrence.

It promises to publish on its website its findings, including any recommendations for measures to improve safety, when it has concluded its investigation.

Greater Manchester’s MetroLink tram service was disrupted over the recent Easter weekend, to allow engineers to carry out upgrade work intended to improve the reliability, capacity and resilience of the city region’s tram network.