Commuters on Massachusetts Bay Transportatoin Authority (MBTA) trains on the Worcester/Framingham lines will be getting a huge Christmas present this year - a new ride to work or home.

MBTA is introducing four new 180-seat bi-level commuter coaches on eleven separate routes this week. On the Worcester/Framingham line, that means four train runs -- numbers 508, 517, 526 and 523 -- each will have an additional double-decker coach tacked on to their regular consist of coaches.

MBTA also will use the new coaches to swap out one single-decker coach for one bi-level coach on eight trains on the Worcester/Framingham line -- numbers 502, 505, 506, 510, 515, 522, 531 and 534 -- and four on the Franklin line -- numbers 737, 792, 796 and 797.

MBTA General Manager Daniel Grabauskas said the added seats and touches like guaranteed bathrooms, which are not on all single-decker coaches, are meant to make riding the commuter rail more attractive. ]

The addition of the new double-decker coaches this week is part of larger project to add a total of 33 new double-decker coaches to the commuter rail system. Fifteen coaches already were added this year to the Old Colony line to Braintree. Another 14 will be added by March, though it is not clear on which train lines those coaches will be used, said MBTA spokesman Joe Pesaturo.