In recent weeks, signs urging people not to “drink and cycle” have been popping up around Seoul. The reason why will be apparent to anyone who visits the capital’s busiest districts on a Friday night, or even a weekday evening.

Seoul is suffering from a dramatic shortage of taxis, a problem that has become so acute in recent weeks that the transport ministry says that three in four people are unable to get a cab late at night.

With buses and subway lines closed after midnight, failing to catch a ride will frequently leave one stranded with no choice but