Is there any signage on the fencing to the effect of do not enter, no trespassing, closed by landowner/railroad/borough, etc.? If not then access=private or access=no would be difficult to support as they describe legality of access, not suitability or ease of access (and for that matter bicycle=no would not be appropriate for a footbridge where there is no bike gutter UNLESS it is outright illegal to attempt to ride or carry a bike across). However, signage or no, if there a barrier with no gate (or locked gate) at both ends it certainly can be mapped and routers will typically take that into account.