Notice how the wheels of this truck appear to be floating above the tracks! This is a fairly new method of transporting trucks by rail without the use of a flatbed car. The truck bodies are only attached at the ends to rail wheel units. Unlike normal freight cars, these can be pulled by a passenger train at high speed.
The photos in this slide show were taken in the mid-1990's by Steve Grande on his Amtrak travels throughout the nation. The size of the photos is purposely smaller as disk space was expensive and download speeds were slower at that time.