The latest agreements reached include with the International Brotherhood of Boilermakers, Blacksmiths, Iron Ship Builders, Forgers and Helpers; the Sheet Metal Workers’ International Association; the National Conference of Firemen & Oilers; and the Brotherhood of Railroad Signalmen.

Current agreements cover roughly 60% of the 132,000 employees in negotiations, implement recommendations of a Presidential Emergency Board appointed by President Obama, NRLC said.

If pacts with the remaining three unions remain elusive during a 30-day “cooling off” period that ends Dec. 6, labor is permitted to strike under the Railway Labor Act. But as in past years, Congress likely would legislate a contract similar to the emergency board’s recommendations if a strike occurred.

The Association of American Railroads estimates such actioncould cost the U.S. economy up to $2 billion per day.