"For anyone who is still up there, it'll be like a whip," said Ahmad Sujadi, of the state-run railway, PT Kereta Api Indonesia. The contraptions will be installed at select crossings this week.
Indonesia has tried just about everything to keep passengers from clamoring atop trains that crisscross its main island of Java: spraying them with paint guns, calling in sniffer dogs, and asking for help from Muslim clerics.
The first tactic that worked was deployed last month.
Grapefruit-sized concrete balls were suspended on chains from a frame that looks like a soccer goal. "Rail surfers," realizing they could be knocked in the head or even killed, quickly called it quits.
The concrete balls can only be suspended over non-electric tracks, but no rail-surfing deaths have occurred where they are in place.
Buoyed by that success, railway officials decided to try the brooms as well.
They'll be set up along the line linking the capital, Jakarta, and the West Java town of Bogor.
Sujadi, who didn't disclose the ingredients of the smelly goop, said he was unaffected by criticism for all the strange and strict security measures.
"Some people say its inhumane, but that's fine," he said. "Because letting them ride on the roofs is even more inhumane."
Hundreds have clamored to the roofs in the past because they want to escape overcrowded carriages, can't afford the price of a ticket, or, simply, for fun.
But dozens are killed or injured every year, falling off the train or being electrocuted by the power lines above.
Since we are on the Train subject, here is an Onion News Network Report.
Breaking News: Woman Crying On Train Platform