The Port Authority has announced quarterly bus-trolley service adjustments to take effect on Sunday, but it's the smallest number of changes in many years.

Only seven bus routes are affected, most of them reducing service to Century III Mall in West Mifflin. For example, 59A West Mifflin-North Versailles weekday trips will now terminate at Wal-Mart but won't continue onto the mall while 51C Carrick service to the mall bus shelter will be reduced to 24 trips.

On the T, minor revisions will be made to the 42C Castle Shannon via Beechview weekday schedule, but the entire Monday-Friday evening schedule has been changed for the 42S South Hills Village via Beechview route.

Full details of the new service changes are on the Port Authority Web site.

Notices have been posted and new schedules have been printed for affected bus-trolley routes, but the overwhelming number of schedules will remain the same. The adjustments are made every three months in order to adjust service to changing conditions and in accordance with union contracts whereby workers can choose assignments based on seniority.