OMAHA, Neb. (AP) — The economy appears strong to the major freight railroads that haul the products and raw materials companies rely on, but the lingering trade disputes could derail business if they continue.

Union Pacific and CSX railroads both sounded optimistic about the economy when they reported hauling 3 percent more carloads of freight in the fourth quarter. Norfolk Southern is scheduled to release its report Thursday afternoon.

Union Pacific CEO Lance Fritz says he still sees opportunity for modest growth in the U.S. economy. Shipments of steel, construction products, intermodal containers and a few other categories look particularly strong.

Edward Jones analyst Dan Sherman says the railroads haven’t offered any indication that the economy is slowing down.