Concerns are growing following several accidents in which the automatic safety mechanisms of elevators did not detect thin objects stuck between the doors and failed to open.
In July, part of a female middle school student's finger was severed by the string of her bag when it got stuck between the doors of a descending elevator at her school in Saitama Prefecture.
The Land, Infrastructure, Transport and Tourism Ministry has sent notifications about the issue to local governments and other organisations, encouraging them to alert elevator users.
The July accident occurred at a middle school in Shiraoka when the third-year female student was getting off an elevator on the second floor. A 5-millimetre-thick string from her shoe bag, which she was holding in her right hand, got stuck between the closing doors as the elevator descended, severing her middle finger from near the base of the fingernail.
According to the school, the elevator's operating system had been set to automatically keep the doors open for about four seconds; manually pushing and holding the relevant button on the control panel inside the elevator could keep them open for longer.
The elevator is normally used to transport school lunches and eating utensils, but the girl used it to accompany her friend, who had a broken leg and was using crutches, from the school gymnasium to their classroom.
According to the ministry, there have been at least five accidents since 1991 in which elevators descended or ascended with a string or other item stuck between the doors. No records of such accidents were kept before then.
In 1991, an 8-year-old boy at a primary school in Ehime Prefecture died when a skipping rope he was holding got caught in the doors of an elevator and strangled him. In 2006, a 95-year-old woman lost four fingers when the dog leash she was holding got stuck between the doors of an elevator.
Current national standards require elevators to be equipped with safety mechanisms that automatically open the doors when a person or object is detected as being caught between them. However, no concrete numerical standards have been set for specifying the thickness of objects to which the safety mechanisms should react.
One major manufacturer's elevators, under its own standards, feature a safety mechanism that opens the doors when an object of about 5 millimetres or wider is caught. However, an official of the firm said the system might fail to respond to something soft, such as a length of string.
Hitachi Building Systems Co., a major Tokyo-based firm in the elevator industry, has developed a safety mechanism that can detect objects measuring 3 millimetres or more. However, this mechanism costs about ¥150,000 (S$1771.3 thousand) more than conventional ones.
"If we increase the sensitivity, it could cause a system failure - unstoppable opening and closing [of the doors], for example - by sensing such tiny objects as a small pebble or even dust," a company spokesperson explained.