Several people with helmets on their heads waiting in line at a sidewalk vendor.
Several motorcycle riders race down the street.
The motorcycle riders are the ones that need a helmet when riding, and the people waiting in line do not.
exists e1 s1 x1 x2 x3 x4 x5 x6 x7.(a_topic(x1) & at(e1,x6) & n_vendor(x6) & of(x6,x7) & n_sidewalk(x7) & in(e1,x5) & n_line(x5) & Actor(e1,x4) & v_wait(e1) & (x1 = x4) & with(x1,x2) & on(x2,x3) & n_head(x3) & of(x3,x1) & n_thing(x1) & n_helmet(x2) & n_people(x1) & a_several(s1) & Theme(s1,x1))
exists s1 x1 x2 x3 x4.(n_street(x4) & a_topic(x1) & down(x1,x4) & n_race(x1) & of(x1,x3) & n_rider(x3) & of(x1,x2) & n_motorcycle(x2) & a_several(s1) & Theme(s1,x1))