The Metropolitan Transit Authority (MTA) is expanding bus Bx 31?s route to include Woodlawn?s main thoroughfare, Katonah Avenue. Officials say the area?s large senior population will benefit from the change. It will also make it easier for bus riders to get to and from Our Lady of Mercy Medical Center. Currently, the bus runs from Westchester Square to Webster Avenue. MTA officials estimate that it will cost an extra $75,000 a year for the expansion, but expects increased ridership will make up the costs over time.