To dream of something being express represents feelings about a situation or option being a quicker. Quick fixes, fast track choices, easier co-operation. An ability to rush something.
Negatively, dreaming of something being represents fears of doing something too quickly. A quicker way to solve a problem that is a lot more dangerous or risky. Alternatively, it may reflect a person in your life that is arrogantly rushing something or cheating to save time.
Example: A man dreamed of riding sweating horses up a hill to avoid having to deal with train that was coming up behind him. In waking life he was having heart issues and was highly motivated to do whatever he could through natural means to avoid an operation. The express train reflected his fear of a “quick fix” operation that he felt may kill him.