If you had to build a bridge, to carry a transit line (perhaps maintenance access but not for regular road traffic) and had to span a fairly long (say 3000 feet) distance, what would be the cheapest method of construction? I know suspension bridges can provide long spans, but are they cost efective?

a suspension bridge has less materials than a hole stell bridge. i supposed for a suspension bridge. 2 steel towers, a steel way, and cables.

for 300 feet - suspension bridge is too big, even for 300 meters is to big.