OAKLAND — Motorists traveling on lower Oak Street and Fairfield Street this week should be prepared to find alternates routes.

CSX railroad crossings there are being replaced this week, requiring the entire roads to be closed, according to Town Manager Kelly Pinney-Michaud.

As part of the work, CSX will install new track in one big section, and new pavement also will be laid, she said.

A CSX scheduling representative told Pinney-Michaud that once lower Oak and Fairfield streets are completed in two to three days, workers will start replacing the Pleasant Street railroad track crossing, a project expected to be completed before school starts, she said.

“They are installing more heavy duty track that can withstand speeds of 40 mph,” she said.

A call to CSX’s media office on Monday was not returned, nor was an emailed message sent to the same department.

CSX Corporation, with subsidiaries based in Jacksonville, Florida, is one of the nation’s leading transportation suppliers, according to its website. The company’s rail and intermodal businesses provide rail-based transportation services, including traditional rail service and the transport of intermodal containers and trailers.

CSX says it has about 20,000 miles of track in 26 states, the District of Columbia and the Canadian provinces of Ontario and Quebec. Its network serves some of the largest population centers in the country.