While the phone is locked, double click the home button and leave your thumb rested on the button for a second. It will set up an Apple Pay payment and leave it

While the phone is locked, double click the home button and leave your thumb rested on the button for a second. It will set up an Apple Pay payment and leave it ready to go. It lasts for 60 seconds before requiring authorisation again. So simply preload the transaction as you're walking to the barrier, then touch your phone on the reader. Usually it is fractionally faster than contactless cards.