Several people are riding motorcycles down a narrow street.
People are wearing helmets.
Just because people are riding motorcycles doesn't mean they're wearing helmets.
exists e1 s1 s2 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & down(x2,x3) & n_street(x3) & a_narrow(s2) & Theme(s2,x3) & n_motorcycle(x2) & n_people(x1) & a_several(s1) & Theme(s1,x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_wear(e1) & n_helmet(x2) & n_people(x1))