There are LEGO bridges with a free span from 10 cm to above 1 meter.
If you only need a short span, you can throw some beams on pillars, but
if you have to span a large gap, a truss
bridge, or a suspension bridge is
needed.
Two companies are competing for the market for small cars that fit on
the roadplates. In addition to their products there are a few "wide" cars
(30-50 LU) on the market.
You can't just build a LEGO bridge. We had to create some
rolling stock for the construction workers. The first thing they wanted
was dining waggons, and then they thought the welding equipment needed
wheels too.
There is also an extra wide monorail train from Bregnerod Bybane.