Canadian National Railway Co (CNR.TO) will buy 200 locomotives in the next three years from General Electric Co, Canada's biggest railway operator said on Friday, to support expected growth and drive efficiencies.

CN, Canada biggest railway operator, is extending a major hiring spree into 2018 as it scrambles to keep pace with demand and fill vacancies, aiming to add at least 2,000 more workers to the 3,500 it hired in 2017.

Montreal-based CN has been doing brisk business in western Canada, hauling bumper crops and intermodal containers to port, and has seen soaring volume of sand shipped for use in fracking shale rock to produce oil and gas.

Through the third quarter, volumes were up 14 per cent compared with the same period last year, CN said, also reflecting gains in coal and automotive shipments.

"We are bullish on the North American economy and on our ability to compete and win new business with our superior service model," CN Chief Executive Luc Jobin said in a statement.

The order is the largest since 2014 among Class 1 railways, the biggest operators by operating revenues, CN said. Delivery is expected to begin in 2018, with the balance of locomotives, produced at GE's Fort Worth, Texas facility, in 2019 and 2020.

In coming years, growth is expected from domestic and international intermodal container shipments, sand and new grain terminals opening on CN routes, the company said at an investor presentation this summer.

CN shares were slightly higher at $104.10 at mid-session on Friday on the Toronto Stock Exchange.