In a video taken by the bystander at around 6.30pm yesterday, a person can be seen crouching on the back of the tram, clinging onto the back of the end carriage.
The tram is moving along at speed, faster than the cars alongside it.
This is known as ‘tram surfing’, which means hanging off the back and sides of a moving tram. It is forbidden due to the fact it is very dangerous.
A spokesperson for Supertram said: "We were shocked and concerned to see this. Our driver was unaware at the time that the incident was taking place.
"This kind of behaviour is unacceptable and extremely dangerous. We are working with the police on their investigation and urge anyone who does witness individuals involved in this behaviour to report it to the police, or a member of staff."