A man wearing an orange safety vest writes in a PDA while standing next to a train.
There is one man in this picture.
A man implies the singular, which is explicit in saying one man.
exists e2 e1 e3 x1 x2 x3 x4 x5 x6 x7.(while(e2,e3) & to(e3,x7) & n_train(x7) & r_next(e3) & Actor(e3,x1) & v_stand(e3) & in(e2,x6) & ne_org_pda(x6) & Actor(e2,x1) & v_write(e2) & Theme(e1,x3) & Actor(e1,x2) & v_wear(e1) & n_vest(x3) & of(x3,x5) & n_safety(x5) & of(x3,x4) & n_orange(x4) & (x1 = x2) & n_man(x1))
exists p1 x1 x3.(n_picture(x3) & exists x2.((x1 = x2) & in(x2,x3) & n_man(x2) & card_eq_1(x2)))