More information about the site:ย https://www.visitinvernesslochness.com/listings/culloden-viaduct
This area can either be completely quiet or hoaching with camper/adventure vans, so use discretion when searching. This area is best explored by bike, so if that's something available to you, I highly recommend approaching the viaduct that way.
There is an open access point right at the trailhead/car park - no need to hop any fences!