OMAHA, Neb. (AP) – The intense heat wave enveloping much of the country is snarling transportation in some areas by causing metal railroad rails and asphalt roads to expand and buckle. Omaha-based Union Pacific Railroad says the heat has forced it to slow its trains in heat-affected areas by 10 to 20 mph. Company spokesman Mark Davis said Wednesday that extreme heat can cause metal rails to expand and kink at weak spots. The triple-digit temperatures have had a similar effect on some asphalt roads, bridges and sidewalks.