Photo/Illutration QR codes on the doors of a subway train at Daimon Station on the Toei Asakusa Line on Dec. 8, 2023 (Yuka Honda)

Seiji Okamoto was getting desperate as his supervisor continued pestering him to come up with a money-saving solution for a new safety project along a Tokyo subway line.

His memory of a Quick Response (QR) barcode reader system for product inventory led to a project that ended his workplace stress and slashed costs by around 99.9 percent.

It will also likely enable the Tokyo metropolitan government to achieve its goal of having safety gates installed on the platforms of all stations on its four Toei subway lines by the end of February.

Three of the four Toei subway lines already have the safety gates on their platforms. They use a radio system to synchronize the opening and closing of the train doors with the opening and closing of the platform gates.

But work on the Asakusa Line had been put on the backburner because the tracks are also used by Keikyu Corp., Keisei Electric Railway Co., Hokuso-Railway Co. and Shibayama Railway Co.

Fewer companies operate trains on the other three Toei lines.

Setting up a radio system on train cars operated on the Asakusa Line would cost the metropolitan government an estimated 2 billion yen ($13.5 million). The other four companies would also have to spend tens of millions of yen for each of their trains.

Another challenge was that the trains would be forced out of service when the radio system was installed.

Okamoto, now 63, who served as acting chief manager in charge of developing technology for platform gates at the time, was tasked with finding an alternative.

He initially thought about using a laser sensor system to control the doors and the gates, but it wasn’t accurate enough.

Okamoto even considered having train crew members manually open the doors, but that method could create longer stops and disrupt subway services.

After thinking about automatic barcode readers, it occurred to him that he could build a system that reads QR codes to operate the platform gates.

Okamoto approached Denso Wave Inc., an industrial equipment manufacturer based in Agui, Aichi Prefecture.

The company offered to help because it saw a possibility to expand the use of QR codes, for which the company has a registered trademark.

One problem was that scanning QR codes on train cars from the front is difficult when passengers are lined up on the platform.

Denso Wave and Okamoto performed repeated experiments to see whether the QR codes could be scanned diagonally.

A safety gate was set up at a station to ensure it worked in sync with a train door.

The procedure was repeated for one month to ensure the system could operate flawlessly, even when it was difficult to read the QR code because of stains and other conditions.

Normally, about 70 percent of the data contained in a QR code must be scanned to restore the remainder.

But Okamoto reduced that ratio to 50 percent.

Asakusa Line stations with platform safety gates now have three cameras above to read the QR codes.

When a train arrives, the cameras scan the 15-centimeter-square QR codes affixed on train doors to open the platform gates.

The cost of putting the QR code stickers on the train doors was only 2.7 million yen.

The metropolitan government said it allocated a total of 11.5 billion yen for the overall refurbishment project from its budgets between fiscal 2017 and 2023 to buy and install the safety gates and cameras.

The government’s Bureau of Transportation and Denso Wave obtained a joint patent for the technology.

With no royalties required, the technology has been adopted by Odakyu Electric Railway Co. and other railroad companies.

Okamoto has been working for the transportation bureau for about 35 years, mainly on technologies to improve train safety.

“I appreciate that I had a chance to develop a technology to protect lives,” he said.

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