Starting Monday, Jan. 7, all MetroLink tickets and two-hour passes will need to be validated by customers prior to boarding the trains, according to a Metro news release.

Ticket-vending machines no longer will automatically print the expiration time on these tickets or passes. This will allow customers the flexibility to purchase Metro tickets in advance of their trip, and then validate tickets when they are ready to use them.

It also will eliminate confusion over whether or not tickets need to be validated, according to the release. The following fares must be validated starting Monday:

• One-Ride Ticket.

• Two-Hour Pass.

• Round-Trip Tickets — each ticket immediately before travel.

• Tickets from 10-Ride Ticket Booklets.

A valid fare is required to ride on the Metro Transit system, the release stated. A passenger with a ticket or two-hour pass must have that validated ticket or two-hour pass in his or her possession as proof of payment. A ticket that has not been validated is considered a fare violation and may result in a citation and a fine.

Some Metro customers receive their tickets and two-hour passes from their school, college or other organization. In those cases, the passenger, not the organization, is responsible for ticket validation, and the passenger would receive the citation and fine for not having a validated ticket or pass.

The validation process is simple, according to the release. Tickets are inserted into one of the red validation machines which are at all MetroLink platforms. A ticket is correctly validated if the day and time appear along the side when the ticket is removed from the validation machine.

Metro volunteer ambassadors will assist customers at several MetroLink stations during the peak morning and afternoon commutes on Monday. Ambassadors will be at North Hanley, Civic Center, Central West End, St. Charles Rock Road, Shrewsbury, Belleville, Delmar Loop, Fifth and Missouri and Emerson Park from 6:30 a.m. to 8:30 a.m. and from 3:30 to 5:30 p.m. Monday.