An Indonesian railway company began hanging concrete balls over train tracks to prevent people from riding on the roofs of train cars, local media reported.

Rail company PT KAI told Indonesian news agency Kompas that in several places, 12 concrete balls weighing three kilograms each (about 6.5 pounds each) were placed just above train height. The balls would deliver a heavy blow to any person’s head attempting to ride on top of a train car.

The concrete ball barrier is intended to deter “mischievous passengers” from attempting the dangerous practice, who are at risk of falling off the train car, Kompas said. Dubbed Goal Bola-bolas, the balls are suspended on soccer goal-like frames installed at various points along the tracks.

A spokesperson with PT KAI, Akhmad Suyadi, told the news agency that the barrier is not intended to harm people but is designed for safety purposes.

Other initiatives to deter passengers from riding atop trains, including spraying them with paint or spreading oil on the roofs, have not worked. Roof riders also face arrest.

At least 53 passengers died in 2008 in an accident concerning people on a train roof, according to the BBC, citing local Indonesian officials. Last year, 11 people died. The most common form of death is by electrocution via overhead power cables, but some have fallen from moving train cars.