BOSTON (AP) — Massachusetts will pay $100 million to buy train tracks from a private company in order to expand commuter rail service west and south of Boston.

The deal announced yesterday between the state and CSX Transportation could take four years to fully complete and still faces hurdles.

The most immediate change will be extending five weekday commuter trains from Boston to Worcester as of Oct. 27.

The plan calls for the state to purchase the New Bedford-Fall River line from CSXT to make it easier to extend commuter rail service there.

Bridges also would be raised and tracks lowered to fit double-stack freight trains.

Lt. Gov. Timothy Murray says the deal is “significant” because it will strengthen links between Boston and Worcester and benefit the economy.