according to the online routing guide, Spring Road has Banbury as a routing point, so only the shortest route is allowed.
The Nationalrail site shows both via Birmingham and Stratford as being ok - via Birmingham is usually the quicker route.
All of the stations on Birmingham to Stratford line have Banbury as a routing point, it could be a bit difficult for passengers to work out the shortest route for the stations in the middle, if I've got the rules correct.
It doesn't really matter to me, I was just looking for a cheeky way of reducing the cost of Banbury to Birmingham!
The Nationalrail site shows both via Birmingham and Stratford as being ok - via Birmingham is usually the quicker route.
All of the stations on Birmingham to Stratford line have Banbury as a routing point, it could be a bit difficult for passengers to work out the shortest route for the stations in the middle, if I've got the rules correct.
It doesn't really matter to me, I was just looking for a cheeky way of reducing the cost of Banbury to Birmingham!