Holders of physical passes must swipe the magnetic stripe on their pass when boarding a bus. Holders of stored value tickets must tap their tickets when boarding a bus. Holders of digital passes must scan their passes in a QR code reader aboard MetroRapid buses, or show the smartphone app red screen to the driver on all other buses. MetroRail operates on a proof-of-payment system; passengers must show proof upon request. Holders of the Reduced Fare ID may be asked to show Id.