People walk down the busy sidewalk.
People happily walk down the sidewalk.
If the sidewalks are busy it does not seem likely that people would be happily walking down them.
exists e1 s1 x1 x2.(n_sidewalk(x2) & a_busy(s1) & Theme(s1,x2) & down(e1,x2) & Actor(e1,x1) & v_walk(e1) & n_people(x1))
exists e1 s1 x1 x2.(n_sidewalk(x2) & a_happily(s1) & Manner(e1,s1) & down(e1,x2) & Actor(e1,x1) & v_walk(e1) & n_people(x1))