Bridges have been around since ancient times to get over obstacles that can't easily be crossed, like rivers or crevasses.
What is the oldest known example of a bridge specifically built to pass traffic over other traffic?
That is, a level junction could have been built and would have been easier, but a bridge (or bonus, tunnel) was built instead.
Excluded are:
Bridges that cross other routes by happenstance or necessity, like a bridge over a canal including a towpath, or a bridge over a steep valley that has a road through it. The crossing of the two travel routes needs to be the primary purpose
Bridges built for security or access control reasons, like a gatehouse in fortified walls.
Bridges to remove the need for a level change - a hallway through an upper floor of a building isn't an 'overpass' merely because there's a hallway on a lower floor below it. The same for a canal-over-river/canal crossing where a bridge avoids constructing locks.
I'm open to any traffic types or combinations that could have crossed at a level. For example, two roads, foot traffic and railway, or even two canals.
Wikipedia gives an example as:
The world's first railroad flyover was constructed in 1843 by the London and Croydon Railway at Norwood Junction railway station to carry its atmospheric railway vehicles over the Brighton Main Line.
It seems likely an older non-railway example exists.
