I would argue it's valid. The appropriate Routeing Points are Newton and Motherwell, for which the mapped route is SR.
Map SR has both a direct link from Newton to Motherwell, which thus allows travel via Hamilton Central or, theoretically, via Uddingston (not that there are direct trains from Newton to Uddingston usually).
But I would argue the direct linjk also permits travel via Cambuslang, on the basis that you aren't actually passing through Newton station again, so it's a traceable route that doesn't involve doubling back through any station. There are no platforms on the WCML 'fast' lines that bypass the station, and on the Sectional Appendix map for the WCML 'fast' lines, the station isn't even shown:
Journey planners won't allow travel via Cambuslang because they are told to treat trains timed at Newton West and/or East Jns as passing through Newton station, thus they deem this to be a route that involves doubling back. But this is probably more intended to prevent routes from
not being validated where Newton forms an intermediate Routeing Point on a mapped route.
I note there are several local easements which allow travel via Cambuslang for similar journeys, but not specifically Newton to Wishaw, e.g.
700867
Customers travelling from Kirkhill, Burnside, Croftfoot, Kings Park, Mount Florida, to Uddingston or Bellshill, may doubleback through Newton (Lanarkshire) after interchanging at Cambuslang. This local easement applies in both directions.
and also 700873, 701037 and 701101.
www.brfares.com
is valid changing at Cambuslang? It's 20 minutes faster to do so on the return. The Wishaw trains do not stop at Newton, and the connection at Motherwell is 30 minutes on return most hours, as the trains leave same time.
