Headway refers to what?

• A. The distance between successive trains at the same location.
• B. The speed difference between trains.
• C. The time separation between two trains traveling in the same direction.
• D. The number of trains per hour.

Answer: (C)

Headway is the time gap between two trains traveling in the same direction. It’s a time-based measure of how often trains follow one another, measured at a fixed point along the line. This is why the best answer is the one describing the interval in time between successive trains. The distance between trains is called spacing, not headway, and a speed difference describes how their speeds differ, not the spacing over time. The number of trains per hour is a frequency, which relates to headway (roughly the inverse of headway in minutes), but it’s not the definition of headway itself. For example, if trains pass a point every three minutes, the headway is three minutes, corresponding to about twenty trains per hour.