Travelling to Dumfries

A paper map will show you and Google also provides the answer - it’s a mixture. As it’s a main route to the ferries and used by HGVs, I think you can establish the feasibility for your purposes👍🏻

We used it in places earlier this year. Primarily single carriageway, but with some dual sections. It’s a major HGV route as well. And likely to be busy with MHs and caravans. If you think back to how the A1 North of Doncaster used to be, before being straightened, bypassing and given extra lanes, then this is what the A75 is like. We used it back in May and had no problems whatsoever, between Gretna and Stranraer, at various points. Likely to be a lot busier at the moment though.

As the others have said, it's a mixture.  Mostly single carriageway but there are some stretches of dual carriageway.  Just be mindful that there is a 40mph speed limit in place for HGVs , so if you just happen to get amongst or behind traffic heading to or from the ferry, it can be a very slow journey!  It's a very scenic road in places, so as long as you allow yourself plenty of time it's not a bad road at all :)

You will find it hard to keep up with the HGV s safe journey 

We have use the A75 recently from the A77 to the M6 and it seemed a perfectly fine road. As we were heading for Garlieston (from Ayr) we did miss out a small section as we did a short cut across country but can't see that the missing bit would be worse than the rest!

David