Roughly 90 percent of Japan's major train operators are prepared to halt services upon receiving a government alert over an imminent threat from a ballistic missile from North Korea, a Kyodo News tally showed Tuesday.

This means such an alert could freeze the country's public transportation systems in an instant, a response transport experts say is necessary to minimize potential damage from an attack but that others say could temporarily paralyze urban activities.

The finding comes after Tokyo Metro, a major subway operator in central Tokyo, suspended train services on media reports of a ballistic missile launch by North Korea in late April and drew criticism for taking an "excessive response."

Among the 31 major operators in the country surveyed by Kyodo, 27 said they will halt services based on information provided by the government's satellite-based J-Alert system or a similar alert system called the Em-Net.

Of these, nine said they will suspend all train services upon receiving an alert of a missile launch even if they do not know where the missile would land.

The government first issues a launch alert under the J-Alert system if it sees the likelihood of a missile flying toward Japan. If the government then determines that the missile may hit the country, another alert is issued calling on people to take cover inside buildings.

Many operators stepped up their preparedness in April amid heightened tensions on the Korean Peninsula, with North Korea test-firing a ballistic missile on April 29 following a slew of similar missile launches and rising concerns about its conducting a sixth nuclear test.

"North Korean missiles are increasingly seen as a real threat," said Seiji Abe, a Kansai University professor specializing in transport policy.

"If a train were to go across a bridge that has been damaged by a missile, for example, it could cause great secondary damage, so halting trains based on J-alert or Em-Net information is the right choice," he said.

"I understand it is aimed at ensuring our safety, but it would be a problem if I couldn't get home as I have a young child," said a 36-year-old working mother, who commutes to her workplace on Osaka Municipal Subway trains, which will be suspended on information of an incoming missile.

Kyodo News interviewed representatives of all six Japan Railway group companies and 16 major members to the Association of Japanese Private Railways as well as nine municipalities operating their own public subway services.

The nine railway operators that will suspend train services upon receiving missile launch information include Tokyo-based Tokyu Corp. and Fukuoka-based Nishi-Nippon Railroad Co.

A total of 13 operators, including Saitama Prefecture-based Seibu Railway Co. and Osaka-based Hankyu Corp., will halt services upon receiving information of an incoming missile to their service areas.

Five other operators said they will also consider other circumstances in making such decisions. They included Tokyo-based Tobu Railway Co. and Central Japan Railway Co., also known as JR Tokai.

Four operators said they have yet to stipulate their responses, including the Kyoto Municipal Transportation Bureau and Transportation Bureau City of Sendai.

While many of the operators said they will take media reports into account in making decisions, none said they will halt services based solely on media reports.

Tokyo Metro decided in mid-April to stop trains when it receives media reports of missile launch information and actually suspended train services for about 10 minutes when North Korea test-fired one on April 29.

But given the impact on users and imbalance with other train operators, it has since decided to make its decision based on the J-Alert system, it said.

Among other notable responses, the Osaka Municipal Transportation Bureau, which operates the Osaka Municipal Subway, said it will stop using subway ventilators to counter possible chemical weapons use in addition to suspending its train service when it receives a call for evacuation after an initial alert.

Sapporo City Transportation, which will stop trains based on information of a missile launch, said its officials will use office mobile phones to receive emergency alert emails as it cannot use the J-Alert system.