A large crowd of people walk, casually, across an elevated road or bridge.
A group of people cross some kind of bridge or road structure.
Group or crows implies a larger amount of people, while saying elevated implies that the road or bridge has a structure that supports it.
exists e1 s1 s2 s3 x1 x2 x3.(across(e1,x3) & (n_road(x3) | n_bridge(x3)) & a_elevated(s3) & Theme(s3,x3) & a_casually(s2) & Manner(e1,s2) & Actor(e1,x1) & v_walk(e1) & of(x1,x2) & n_people(x2) & n_crowd(x1) & a_large(s1) & Theme(s1,x1))
exists e1 x1 x2 x3 x4.(Theme(e1,x3) & Actor(e1,x1) & v_cross(e1) & of(x3,x4) & (exists x5.(n_structure(x4) & of(x4,x5) & n_bridge(x5)) | exists x6.(n_structure(x4) & of(x4,x6) & n_road(x6))) & n_kind(x3) & of(x1,x2) & n_people(x2) & n_group(x1))