What does an umpire do, and what should I watch for?

Umpires are the referee's assistants. They watch for and report infractions, but don't make decisions. The referee or head umpire assigns their positions.

Signaling: raise a yellow flag to show an infraction or incident, then report it to the head umpire or referee. A white flag may be used to signal all clear.

Common infractions:

• impeding or jostling, and unfair assistance or contact
• in straightaway races, running out of the assigned lane or interfering with another runner (interference doesn't require contact)
• in races in lanes around a curve, running on or over the inside lane line
• in races not in lanes, cutting in without being a full stride ahead of the runner whose path is crossed, or deliberately running on or inside the curb to gain a meaningful advantage (Rule 5-13-1, 2025)
• passing the baton outside the exchange zone
• illegal hurdling, including running around a hurdle or over one not in the assigned lane, or displacing any hurdle by hand (Rules 5-14-1, 2)

The referee decides protests using allowable evidence such as an umpire's written report, so record what you saw and where you were.