London residents who are MasterCard customers and use Apple Pay will be able to ride the Tube for free over the next three Mondays, as part of a promotion by the credit card company to incentivize its users to ditch their plastic cards for smartphones. This is the second time MasterCard has offered "Fare Free Mondays."

To take advantage of the free rides, Londoners must have their MasterCards added to their Apple Pay wallets in their iOS devices. Thanks to the London Underground's contactless ticketing system, which was installed in 2003, riders need only authorize Apple Pay on their NFC-equipped phones and then tap them at the turnstile to take free rides. The promotion is being offered February 29th, March 8th, and March 15th.

Lately, MasterCard has positioned itself as a leader in contactless ticketing for public transit systems. In addition to its work with the London Underground, the company is partnering with a company called Masabi to combine the former's MasterPass payment technology with the latter's mobile ticketing platform. The two companies announced last year that it had deployed its electronic ticketing system for transit riders in Athens, Greece. And later this year, they hope to bring a similar system for New York's Metro North and Long Island Rail Road under an accelerated plan announced by Governor Andrew Cuomo last January.