Union Pacific Corp. has laid off or reduced hours for 1,500 engineers and conductors because of the struggling economy.

Mark Davis, spokesman for the nation's largest freight railroad, said Saturday that the cutbacks have been ongoing since January 2007.

He said the numbers have varied since then, mostly because of the economy and fewer rail shipments.

The Omaha, Neb.-based railroad employs 21,000 engineers and conductors in its 23-state system.

Davis said 1,500 have been affected by the reductions, with 40 percent of those workers being laid off.

The rest are enrolled in a reduced-hour program that allows eight shifts per month.