Steel grid - two or more traffic lanes (# in parenthesis is for bridge with one lane)):
Less than 4" thick: s/4 (4.5 )
4" or more: s/5 (6 ); If S exceeds 10.5'(6 ) use footnote f.
Fotmote f: In this case the load on each stringer shall be the reaction of the wheel loads, assuming the flooring between the stringers to act as a simple beam.