People standing and city on a train or bus.
People are using mass transit.
Mass transit implies a train or bus, and people use it by standing or sitting.
exists e1 s1 x1 x2 x3 x4.(a_topic(s1) & subset_of(x3,s1) & on(x3,x4) & (n_train(x4) | n_bus(x4)) & n_city(x3) & subset_of(x1,s1) & Actor(e1,x2) & v_stand(e1) & (x1 = x2) & n_people(x1))
exists e1 s1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_use(e1) & n_transit(x2) & a_mass(s1) & Theme(s1,x2) & n_people(x1))