How randomised are the splitting options selected by ticket split sites?

[TUC]

Something I have noticed on several occasions (in this case in relation to Trainsplit, but the same may well apply to other sites which offer ticket splits) is if, after seeing the initial menu of journeys/prices, I select Earlier or Later, and then revert to my original list, it can be a different set of options which are now shown, with a different journey and/or a different price shown as the cheapest.

Of course, it is possible that the quota for a particular ticket sold out in 60 seconds I was looking at the Earlier/Later journeys, but that seems unlikely. It therefore makes me wonder to what degree on any search one is only seeing a selection of possible cheapest options?

 

[Adam Williams]

The rail industry's reservation system that has to be used for Advance availability enquiries is currently incapable of communicating enough information to allow an exhaustive search of splits.

As such, various heuristics have to be used and "rationing" applied to the number of lookups that take place when determining availability of Advances involving intermediate stations.

Historically there has also been some non-determinism in the fares engine when fares are identically priced.