A race queen is a model who serves at motor races as a sort of cheerleader. Her actual job is to assist the driver by holding an umbrella over him while his car is worked on, but race queens are generally there to increase the sex appeal. They typically wear short, tight, one-piece dresses (or a two-piece with a short top and mini-skirt) that have the colors of the race team the girl is on that year, along with the name of the team.
In America, they are known as "booth babes".
Occasionally, a gravure idol will cross into the race queen world (and vice versa).