BOSTON (AP) — The Boston-area public transit system is adjusting some bus and trolley schedules this winter and launching an aggressive recruitment campaign in response to a shortage of drivers.

The Massachusetts Bay Transportation Authority said Tuesday many bus routes will operate with less frequency and a select few will operate with more frequency starting Dec. 19.

Charges are also coming to the Mattapan Line trolley service. There are no schedule changes on the Red, Orange, Blue, and Green Lines.

In response to the worker shortage, the MBTA has gone to more than 20 career fairs this fall and is updating and streamlining the way it hires.