The Chippenham to Swindon buses are clockface, at xx35. From experience if a bus is full they'll send it early.

GWR^▸ (Great Western Railway) help says


Which - if I paraphrase - means that "the bus from Chippenham to Swindon leave a few minutes after the train from Bath arrives, and that's what the timetable's based on".  Or put more cynically: "tough luck that the train from Westbury doesn't connect - it's other connections we've look out for".

The train service is usually every 30 minutes on a Saturday ... why not run the replacement bus every 30 minutes, then the connection times wouldn't be a problem, and journey times would be about an hour (Melksham to Swindon example).  Sure - that's more than twice the normal time, but it's understandable and explainable.  Dumping people at Chippenham for over half an hour could suggest something of a lack of caring for customers ...

With a wait of over half an hour, I doubt we'll be dumping 45+ passengers off - irrespective of how close to that the numbers would be getting if the train went through.

Plenty of space available for bus parking.

I can understand the decision, but that doesn't mean I agree it, nor the message it sends to customers.

There may be multiple buses running in each hour - but as a convoy / on the same schedule on Saturday.   I hope so; correspondence for the week has suggested a mixture of low floor buses and coaches from Chippenham to Swindon, with a request noted that at least one vehicle on each run be low floored.   The proportion of "classic" disabled wheelchairs - certainly on TransWilts - is not high, but there are so many very young children with their pram / buggy / wheelchairs who are regular user outside the peak; lots of bags, etc.   Low floor taxis could be sourced as backup - except that the CabFind system that's being used has only got 2 low floor vehicles registered based in Chippenham (26 in Swindon) according to my data.  There are more if you draw a 10 mile radius circle to look.   

Even finding a taxi at Chippenham Station for Rail Replacement duties can be problematic (45 minutes the other week - mid week, mid afternoon, nothing special going on) took 45 minutes for able bodied passengers when the connection from Bristol into the 15:29 to Westbury failed.  Taxi drivers at Chippenham try to avoid taking the "white chits" for GWR^▸ (Great Western Railway) journeys; reported to me that it's because payment is a bit slow.  Very embarrassing for passengers to be hanging around while the alternative is found (and for readers not familiar, the next train isn't yet until 17:53)

You'll find I'm writing statements of issues here, and not providing solutions.   Where a carefully worked train timetable (Simon and his team are experts at knitting connections by rail together in the public schedule) has one of its legs replaced by buses with journey times up from 15 minutes to between 40 and 50 minutes, added to which needs to be a change time, it's not going to be the same level of service as normal, and there will be compromises to be made.  I do have a number of "what about ... if"s I would ask during an informal chat and if (based on local knowledge) they resulted in some tweaking next time, so much the better.

Here's the official GWR explanation ... asked on Twitter of GWRHelp; reply took 80 minutes which I take to indicate that the answer was researched / thought through rather than being one of those questions for which the answer was easily to hand.