The pilot, called "Pink Light," focuses on pregnant women, and is a collaboration between Busan City and Daehong, a Korean PR company. It consists of two parts: a small beacon that women carry around, and light-up signs installed on trains. Women can pick up beacons at certain locations around the city, and they last six months before their batteries need replacing.

Once a woman has a beacon, she only needs to carry it around, and the tech will do the rest. When she's standing near to a seat, the pink light illuminates, letting people know that someone who needs a seat more than them is on board. Once the system detects the woman is seated, the light switches off. As well as clearing up any confusion as to whether a person is pregnant, the system is also helpful at peak hours, where those seated might not even be able to see someone that's just entered a train.

Only a single train line was covered by the pilot, but Busan now wants to expand Pink Light to cover all of its metro and bus systems. While this campaign is just for pregnant women, the underlying technology would obviously be applied to any group -- it's easy to see this working well with the elderly or otherwise frail, on an opt-in basis.