Goatboy said:
No, but if its the SAME TRAIN involved then the capacity constraints are the same!
A London to Brockenhurst passenger is on the train from London to Southampton first!
Obviously Southampton has significantly higher traffic levels but if this is such that it fills the train to bursting from London then there isnt any special room for Brockenhurst passengers either, is there?
The trains aren't normally full to bursting outside the peaks, but they are well loaded. If there is spare room on the trains to/from Southampton then it makes sense to offer cheaper advance fares to encourage more people to use them.
The fact these cheap fares are offered from destinations further along the line than Southampton implies that SWT feel there's enough Southampton traffic already, but they'd like more people to/from Brockenhurst onwards to be using the train. A service is generally more profitable if you can get as many bums on seats as possible for the entirety of the journey, rather than having it empty half the time and crush loaded the other half.
I suspect there are other factors in this, too. Brockenhurst is more of a tourist attraction than Southampton, given it's in the new forest (the same can be said for places by the sea like Weymouth). Perhaps these advance fares are aimed mainly at tourists, rather than the commuting traffic from Southampton?