Strolling as a break from my screen, I spotted this bridge not a million miles away from where I live.
On the top is a double-track mainline railway, the Birmingham to London line. The other side of the bridge is a farm that I recall from my Ministry of Agriculture days as belonging to a pig-keeper called Mr Hoare. This side there is a very newly built housing estate.
As a prototype, it's got a lot going for it. No complicated brickwork for the arch for a start. Some scribed plastic painted concrete colour and weathered would do the job. Looking at the modular construction, I'd say this could be extended to a 4-track line too or possibly reduced for single-track.