Melanie Kirkpatrick compares it to Harriet Tubman’s:

The way it’s set up is similar. The safe houses and transit routes are kept secret and vary a lot. There is another similarity in that many of the people who operate on the underground railroad are ethnically Korean, just as many of the operators on the original underground railroad were free blacks. Another similarity is that the enslaved person has to make that initial decision to leave. It’s very difficult to get access to a person in North Korea and talk to him about getting out. In many cases the North Korean has to make that decision on his own and make his way to China. That’s changed some in the past couple of years. There are now brokers and missionaries that have contacts that help them reach into North Korea and get people out. And once they get to China another set of operators take over.