Railway staff in Indonesia have started hanging concrete balls above the tracks to try to prevent commuters from riding on the roofs of trains.
The balls are being installed just above carriage height near a station outside the capital, Jakarta.
More will be put up elsewhere if they are found to keep people off the roofs, the BBC reports.
Previous attempts to deter roof riders included spraying roofs with paint, spreading oil on carriages and hiring musicians to perform safety songs.
BBC correspondents say those initiatives have failed.
Roof riders also face the possibility of imprisonment..