Here is how this artist rendered Brunel's Saltash Bridge:
Here is how it appears today.
Did the appearance change, or was some artistic licence taken in the painting?
My question is: Did this artist take some licence with the Royal Albert Bridge - or has its appearance changed?
Probably artistic interpretation. #i see the differences you are alluding to but they don't look like things you could reasonably alter in a structure.
The artist's rendering looks like an engraving or etching and as such the final image would have gone through several stages probably starting with a sketch in the field in pencil or watercolours before being worked up into a more detailed composition and then being adapted by the engraver.
At each stage there would have been some degree of interpretation to produce a pleasing composition as well as practical limitations imposed by the processes used. It is certainly not uncommon for landscape artists to idealise scenes a bit and engravers would need to interpret the image to convert it into a printable grey-scale format.
https://commons.wikimedia.org/wiki/File:Royal_albert_bridge_hist.jpg
The picture from when the original was being jacked into place shows the lens closed at each end.
The engraving would have been from before the bridge was constructed -- perhaps while the railway corporation was trying to raise money.
