Just for the record, 23 on today's lunchtime train between Trowbridge and Melksham, with a less impressive 12 on the return at 14.49.
Welcome, Chris. Yep - it gets busier and it seems that most of the trains do. On a brutally cold evening last week, with rain / snow in the air, I dropped off customers at Melksham station for the late afternoon train to Swindon. The waiting shelter was full and the best extra on offer was the covered cycle bar area.
As far as I'm concerned, the statement that the trains aren't used is very much an old wive's tale. It MIGHT have been justified five years ago when ticket sales (the only stats I have that stretch back) were at around 12% of their current level. But is the current usage "ligh" or "low" which seems to be the current test of "should the service be offered" - at least we're given this statement as the reason.
Alastair Darling is quoted as saying that "if a line only has 2 passengers on it a day, it should be replaced by a taxi" - I'm writing that from memory so, PLEASE, anyone correct it but I think I have the gist. I KNOW I have the number right. Wessex trains (on their web site) talk about the number of trains they run per day and the number of passengers, and dividing one by the other I learned that they AVERAGE 50 passengers per train through the whole length of their journey. So your 23 from Trowbridge to Melksham ... and in say half a dozen from Westbury to Trowbridge, another 5 joining at Melksham and another 10 at Chippenham and you're over 40 on board at some point on the journey - only slightly below average. Taking the Southbound services which run through to Southampton, they are WAY over average (this statistics is skewed in favour of longer distance trains).
The big problem is that the one question never answered by anyone who's any form of decision maker seems to be "What do you consider to be low useage below which a service is not justified" - in other words, we don't know what we're aiming at as the goal posts haven't been defined and can be moved.
I note that Wales and West brought in the Swindon to Southampton service, as far as I can tell, in 2001, without additional subsidy. And it has more or less remained - certainly the service frequency has - as it has grown. This points to a commercial faith which is rather backed up by the other figures on this site. It probably doesn't include any huge profit which is the real problem, since the current bidding process is looking for bids that pay the government chunks of money for the honour of running our train - in other words, a hidden tax on rail travel.
Chris - I appear to have hijacked your comment slightly; I took the opportuniy to put your figures into an element of context as much of the current franchise awards / discussions are based on finances and figures which are not made as available as they could be.