an ambulance drives on the street.
The ambulance is en route to a call.
ambulance driving on a street does not imply it is en route to a call
exists x1 x2 x3.(n_street(x3) & a_topic(x1) & on(x1,x3) & n_drive(x1) & of(x1,x2) & n_ambulance(x2))
exists p1 x1.(n_ambulance(x1) & exists x2 x3.(en(x1,x2) & to(x2,x3) & n_call(x3) & n_route(x2)))