I have read quite a bit on AI work for MM on similar MM threads on dioramas etc and would like to offer a thought on this work which is afterall the purpose of this thread.
Regardless of who made the model a couple of extra things that we could all learn from apart from that mentioned in previous posts is this:
1] In my experience of wooden bridges in oldish structures there is wearing of the wood where the bridge stops and the roadway/track starts. In a newish bridge this would not be the case.
2] When the tyre/rim of the wagon/vehicle leaves a hardish surface and interfaces with a softer material, like the roadway, a bounce occurs which chews or wears down the softer surface leaving a hollow or track to form. This results in puddles etc in rainy weather.
3] If the bridge timber has been exposed to the elements/weather for some time the wood changers colour, maybe bleaches out etc. Allso the wood would attract dirt which in turn may attract seeds etc which may add a bit of green stuff or lichen and moss.
Quite often soils have sand, maybe pumice and the likes which cause general wear and tear etc.
I think that we can all learn from what others say about all kinds of models, I know that I do.
The one thing about MM and AI is that examples are being produced which is more than what I am currently doing so I applaud them for that.