Dutch railway company NS on Monday launched a service to alert rail travellers if they forget to swipe their public transport smart cards after completing their journey.

People who sign up for the service will be sent an email warning them they have forgotten to scan their cards on leaving the train and explaining how they can get back the cash.

Train travellers who don’t check out automatically have €20 deducted from the balance on their cards.

NS is also experimenting with apps which alert passengers to their mistake while still in the station. Passengers who sign up for the service will also have to give the NS permission to monitor their individual journey pattern.

In 2014, passengers on trains, buses and trams failed to check out 7.3 million times, costing them €16m.