SAPPORO - A power outage that halted operations on the Sapporo Municipal Subway on November 3rd was caused by an aluminum-coated balloon. Investigations have revealed that similar troubles have occurred across various transportation systems in Japan.
The blackout on the Tozai Line stranded around 82,000 passengers after a passenger’s balloon came into contact with power lines. According to the Sapporo City Transportation Bureau, the balloon was blown by the wind and touched overhead wires, causing a short circuit. The scorch marks from the contact were clearly visible. Officials said safety devices were triggered, leading to the shutdown of power. It was the first time an aluminum balloon had caused a power failure on the Sapporo subway.
"We’ve never had an incident like this before, so determining the cause took time," said Hironobu Kamata, chief of the Power Section at the Sapporo City Transportation Bureau. "Since aluminum balloons conduct electricity, touching overhead lines can cause the same kind of failure as this one."
Because the Tozai Line has overhead wires, it is particularly vulnerable to interference from airborne objects such as balloons. "On the Toho and Tozai lines, the overhead wires are mounted on the ceiling, while on the Namboku Line, they run along the sides of the track," Kamata explained. "If you drop something, please ask station staff to retrieve it for you," he added.
Similar issues have also occurred with Sapporo’s streetcars. In August 2025, a driver spotted a balloon tangled in electrical wiring, forcing a temporary suspension of service. According to the Sapporo City Transportation Promotion Corporation, although a balloon’s contact with the lines would not cause a power outage, it could still affect operations, prompting daily safety inspections.
Tokyo’s subway system has also experienced multiple balloon-related incidents. According to Tokyo Metro, 24 aluminum balloons have been found inside station premises over the past five years.
While balloons are a common sight at festivals and events, authorities are urging caution when carrying them on public transport, as they can pose unexpected hazards to the power infrastructure.
Source: 北海道ニュースUHB
