People riding escalators.
People ride the escalator up.
Some people ride escalators down, not up.
exists e1 x1 x2 x3.(a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_ride(e1) & n_escalator(x3) & (x1 = x2) & n_people(x1))
exists e1 s1 x1 x2.(n_escalator(x2) & a_up(s1) & Manner(e1,s1) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_people(x1))