A woman was trapped under a tram with serious injuries. Crews released the woman, who was then transported to hospital by ambulance.
The woman became trapped after the horses bolted whilst pulling the tram along the tracks within the site. Ambulance teams were also at the scene. More photographs of the aftermath of the incident here.
The railway was holding a Festival of Transport weekend with traction engines and other attractions on show.
The YEP has also carried a brief report on the incident.