KA 225 had departed Rangkasbitung Station in what was then West Java province, bound for Jakarta Kota on the city's north side. It was a Monday morning, and the carriages were packed with commuters. The route ran through Serpong and then Sudimara, where KA 225 was scheduled to pass KA 220, a fast train running from Kebayoran toward Merak. The system for managing this crossing was entirely manual: station officers communicated by telephone, confirmed track conditions, and gave hand signals to engineers. There were no automated interlocking signals, no digital fail-safes. Everything depended on human beings making the right calls in the right sequence. At Serpong, the stationmaster permitted KA 225 to proceed without confirming conditions at Sudimara -- the first link in a chain of errors that no one would be able to break in time.

When KA 225 arrived at Sudimara, stationmaster Djamhari found all three tracks occupied: KA 225 itself on the first lane, a cement company train on the second, and a headless freight train on the third. There was no room to pass. Djamhari ordered the engineer to move his train to the first lane -- a repositioning maneuver, not a departure order. But the engineer, Slamet Suradio, interpreted the instruction as clearance to continue the journey. An illegal boarder on the platform compounded the confusion by giving what appeared to be a confirming gesture. KA 225 began to move forward, picking up speed toward Kebayoran. Five minutes later, Djamhari's telephone rang. Umrihadi, the officer at Kebayoran Lama Station, informed him that KA 220 had already departed heading straight for Sudimara. Djamhari looked up to see KA 225 pulling away. He sprinted after it, waving a red flag, but the train was already moving at 50 kilometers per hour. A switcher who had boarded the last carriage tried to push through the packed train to reach the engineer. The crowds inside made it impossible.

The two trains met head-on near the Bintaro Highway curve, between what would later become Pondok Ranji Station and Tanah Kusir Cemetery, roughly 200 meters past the Pondok Betung crossing. The impact produced a telescoping effect -- the carriage directly behind KA 225's locomotive crumpled inward, compressing the passengers inside. Most of the 139 people who died were in that carriage. Both locomotives, Henschel-built models designated BB303 and BB306, were destroyed. Hundreds more passengers suffered injuries. The collision happened in a densely populated area of South Jakarta, near what is now Public High School 86, and rescue efforts drew on the surrounding community as well as emergency services. The sheer number of casualties overwhelmed local hospitals.

The courts convicted Slamet Suradio, the engineer, of negligence causing death and sentenced him to the maximum penalty of five years in prison. He maintained that he had simply followed what he understood to be the stationmaster's instructions. After serving his sentence, he received no pension despite more than twenty years working for the state railway company. He returned to his hometown of Purworejo in Central Java and became a cigarette seller. Conductor Adung Syafei received two years and six months. Umrihadi, the Kebayoran Lama officer, served ten months. The question of systemic responsibility -- why a railway carrying millions of passengers still relied on telephone calls and hand signals -- received a different kind of answer. Indonesia's National Transportation Safety Committee recommended upgrading the signaling from mechanical to digital systems and reviewing the railway's standard operating procedures entirely.

One of the investigation's most concrete outcomes was the recognition that the 13-kilometer gap between Kebayoran and Sudimara stations was dangerously long -- too great a distance for manual signaling to manage safely, with too many blind spots along the route. The committee recommended constructing an intermediate station to provide a safety checkpoint. That station became Pondok Ranji, which opened in 1990, three years after the disaster, at almost exactly the spot where the collision occurred. The crash also embedded itself in Indonesian popular culture. Iwan Fals, one of the country's most celebrated singer-songwriters, wrote a song titled '19/10' in reference to the date. Ebiet G. Ade composed 'Masih Ada Waktu' -- 'There's Still Time.' A 1989 film, Tragedi Bintaro, dramatized the event. For commuters who ride the line today, Pondok Ranji Station is an ordinary stop. For those who remember October 1987, it is a memorial that operates every day.