A person dressed in a green protective suit is riding an all terrain vehicle across a desert.
An atv speeds across a desert, its rider wearing a protective suit.
A person on the all terrain vehicle would be considered a rider.  ATV is another name for all terrain vehicle.
exists e2 e1 s1 s2 x1 x2 x3 x4 x5 x6.(across(e2,x6) & n_desert(x6) & Theme(e2,x4) & Actor(e2,x1) & v_ride(e2) & n_vehicle(x4) & of(x4,x5) & n_terrain(x5) & in(e1,x3) & n_suit(x3) & a_protective(s2) & Theme(s2,x3) & a_green(s1) & Theme(s1,x3) & Theme(e1,x2) & v_dress(e1) & (x1 = x2) & n_person(x1))
exists e1 s1 x1 x2 x3 x4 x5 x6.(a_topic(x1) & rel(x1,x4) & Theme(e1,x6) & Actor(e1,x5) & v_wear(e1) & n_suit(x6) & a_protective(s1) & Theme(s1,x6) & (x4 = x5) & n_rider(x4) & of(x4,x1) & n_thing(x1) & across(x1,x3) & n_desert(x3) & n_speed(x1) & of(x1,x2) & n_atv(x2))