The workers had been spraying herbicide near the tracks. Railway rules require lookouts to wave a flag when a train approaches; the driver then sounds the horn and the workers must move away from the line.

Railway officials said they do not know why the workers stayed on the track or what the lookouts did, and they suspect a miscommunication. Because fatal train accidents are very rare in Japan, this incident highlights the need for clear signals and quick evacuation.

Train service on the line was stopped for several hours and then resumed later that day. Takao Suzuki, head of Tobu’s railway business division, apologized and promised stronger safety checks.