Following a successful trial, the city of Busan in South Korea is now planning to introduce a bluetooth-powered system for helping pregnant train and bus passengers who need to sit down.
Round pink lights next to priority seats in train carriages are activated by a sensor carried by pregnant travellers when they board the train.
It was tested by 500 women in April.
Busan now hopes to extend the scheme across train and bus lines by the end of the year, reports Reuters.
Many pregnant travellers say they have difficulty getting seats on public transport at peak times, while other passengers say they are not always sure whether someone is pregnant, especially in the early stages, and they don't want to cause offence by asking.
Busan's solution takes the form of a bluetooth sensor, which has a six-month battery life, that is attached to the outside of a bag or coat of pregnant women who choose to get one.
The original Pink Light Campaign trial (website in Korean) was a collaboration between the city council and local businesses.
In the UK, pregnant travellers on the London Underground can choose to wear a badge which reads "Baby on board" to alert fellow passengers that they may need to sit down.
However, some women are not happy about publicising their pregnancies.
"I found the level of attention embarrassing when I wore the 'Baby on board' badge - I'm not sure how comfortable I would feel with pink lights going off when I got on a train," said Ellie Gibson from parent podcast Scummy Mummies.