In general, fare gates in public transport do not open unless passengers validate their ticket. This practice, which intends to guarantee payment of use, is implemented in the vast majority of subway systems around the world. Metro de Madrid, however, is thinking of applying another approach already existing in Tokyo: open-door validation. The Spanish...
Open-door validation tests in Metro de Madrid
Fare gates remain open permanently and only close when someone does not validate their ticket
Metro de Madrid. @metro_madrid