On this day, 70 years ago, the worst tramway accident in Zagreb and one of the worst in the world occured at Mirogoj line. 19 people died in the accident, and 37 were injured.

The accident happened on a Sunday morning about 8:30 AM when a runaway M-24 tram #21 lost control while riding down Mirogoj Road and crashed in a right turn just before Gupčeva zvijezda intersection.

Mirogoj line was a steep uphill line, with gradient of over 90‰, which led to main cemetery in Zagreb. The line was at the day of accident especially busy due to upcoming All Saints' Day.

The tram operated on route 13 between Mirogoj and Šoštarićeva street and carried about 60 passengers. Departing from Mirogoj cemetery, the driver released the brakes, but upon entering first curve he realised the brakes had failed. Further attempts to slow the tram down were unsuccesful, and it ran downhill without control, reaching speed about 80 km/h. At the last curve before Gupčeva zvijezda, the tram derailed, overturned and struck several trees and a street light. Thirteen passengers died at the scene, with further six succumbing to injuries in hospital. 37 people, including the tram driver, were injured, most of them seriously.

During investigation, it was discovered that prior to the accident the tram had another incident when it collided with a horse-driven wagon, howewer due to no damage occuring the driver was ordered to continue driving to Mirogoj. It is believed that this previous incident contributed to the disaster, due to most of the sand being used up. However, the investigation concluded with the driver being blamed for the accident.

Mirogoj line was closed immediately after the accident, and was out of service until 1964 when it reopened, but only briefly. It was closed permanently in 1967 and dismantled in 1970.
Tram 21 involved in the accident was rebuilt and remained in service until 1974.

At the crash site, a small temporary memorial plaque was erected in 2004, which was later replaced with a stone one, depicted on the photo.