I absolutely believe that visualization will improve performance in track and field. In fact, many professional athletes from golfers and bobsleders to basketball players and gymnasts have been known to use visualization. You could visualize the proper body mechanics for your event or visualize the feeling and sensations of winning the event. Either way, visualizing your self succeeding will build your confidence, which is vital in any sport.
I personally believe that the unconscious mind is unable to distinguish between reality and imagination (so long as the imagination is vivid and detailed). Given this, it makes sense to me that visualizing your self succeeding in a sport would be beneficial. Besides, you can use visualization anytime and anywhere so why not?