Is there an easement that allows this doubleback? It seems to add about 10 miles to the journey.
I have been travelling to the South West from Kings Norton with through tickets for the past 30 years, and have never had a problem "doubling-back" to New St.
Here are some interesting points:
1) The Anytime Return fare to Cheltenham from Kings Norton, New St, Wolverhampton, Birmingham International, Blake St and many other stations in the Birmingham area is £36.50. The same ticket type from Barnt Green and Redditch is £40.00. Kings Norton has Routing points of Birmingham Group and Barnt Green.
2) Easements in the area that I have found are:
86 - Journeys to Alvechurch, Barnt Green and Redditch via Ashchurch may double back from Birmingham New Street or University. This easement applies in both directions of travel with fares routed Any Permitted or Bristol.
300370 - Customers travelling from Selly Oak, Bournville, Kings Norton, Northfield and Longbridge via Bromsgrove may travel via Barnt Green. This easement applies in both directions.
300420 - Customers travelling from Barnt Green via Cheltenham Spa may travel via University. This easement applies in both directions.
300422 - Customers travelling from Bromsgrove via Cheltenham Spa may travel via Birmingham New Street. This easement applies in both directions.
700108 - Customers travelling from Bromsgrove to Birmingham New Street and beyond may travel via Barnt Green. This easement applies in both directions.
700128 - Allow a double back between Bournville and University for journeys between Bournville and Worcester Stations
700189 - Customers travelling from Hereford, Ledbury, Colwall, Great Malvern,Malvern Link, Worcester Foregate Street and Worcester Shrub Hill to Cheltenham Spa and beyond, may not travel via Bromsgrove. This easement applies in both directions.
700248 - Customers travelling from Five Ways or University via Bromsgrove in possession of tickets routed "Not Via London" may travel via Barnt Green.This easement applies in both directions.
3) On a weekday there are only two departures South-west bound that can be connected into from Kings Norton. These are the 7:41 from Barnt Green to Great Malvern and 8:18 Barnt Green to Hereford. Only two trains stop at Barnt Green in the return direction - the 16:49 and 18:49 arrivals from Hereford.
The Easements are a bit of a dog's breakfast, but to me the intention is clear: because of the poor service from Barnt Green to Worcester and Cheltenham, if you have a ticket to Bromsgrove and beyond from any station between Redditch and Five Ways you may double back to New St. To me this is sensible and practical. Tweaks may be needed when the Crosscity service is extended to Bromsgrove, but I would hope the double-back remains for journeys to Ashchurch and Cheltenham and beyond.
For me the clue is that it's more expensive from Redditch and Barnt Green to Cheltenham, than further North - the assumption is that you will travel further (ie to Birmingham) even though you start much closer to Cheltenham!
To TrainMiser: I still believe the £4.10 does not need to be paid.