People sitting on a bus at night.
There are people riding a bus.
if the people are sitting on a bus, that implies they are riding a bus.
exists e1 x1 x2 x3 x4.(a_topic(x1) & at(e1,x4) & n_night(x4) & on(e1,x3) & n_bus(x3) & Actor(e1,x2) & v_sit(e1) & (x1 = x2) & n_people(x1))
exists p1 x1 e1 x2 x3 x4.((x1 = x2) & Theme(e1,x4) & Actor(e1,x3) & v_ride(e1) & n_bus(x4) & (x2 = x3) & n_people(x2))