Canadian National Railway Co. (NYSE: CNI) said Thursday it will spend an undisclosed amount of money to buy 161 locomotives to accommodate anticipated traffic growth over the next two to five years and boost operational efficiency.

The Montreal-based transportation company, which has a fleet of about 1,900 locomotives, will buy 65 new high-horsepower locomotives as well as 96 second-hand high-horsepower locomotives that will be upgraded.

The new and used motive power will enhance operational efficiency and reduce fuel consumption by permitting the retirement of older, high-maintenance locomotives and the cascading of less fuel-efficient main-line units into less-demanding yard and local switching operations, while providing additional locomotives to accommodate increased traffic, Keith Creel, executive vice-president and chief operating officer, said in a statement.

The railway, has a network of about 20,000 route miles that span Canada and the United States, said in its fourth-quarter 2011 report that it plans to buy locomotives that are more fuel efficient than the ones they replace.

Shares of Canadian National Railway fell $1.48 to $77.95 in late afternoon trading.