You guys that are lucky enough to use an RDC toilet (grubby and revolting as they might be) may not need to respond as all your needs are catered for. 
Others that are hardier and made of sterner stock may just know the answer.
When parked up for the night in a lay-by or other such place, how do you guys have a dump when there are no loos about?
Squat by the wheel and hope nobody strolls/drives by?
Take a folding frame with a bog-seat and dog-poop-bag attachment and cover yourself with a poncho for some privacy?
Find or dig a suitable rabbit hole?
Clench your bum sphincter and â– â– â– â– muscles 'till you reach civilisation or MRSA?
Or another solution?
I’ve never needed to stop anywhere outdoors to vacate my bowels. Depending on where you are driving there are plenty places to stop, assuming you are not ill or are feeling the effects of last nights curry, nandos, dodgy pie etc. the longest stretch of road I see without services is about 40 miles.
It did remind me of going for a shovel recce on exercise in the army though, off into the woods, squat against a tree, air blowing around the hydraulics. It’s one of the few things I miss about the army, I might just get myself a small shovel next week.
A combination of red bull and last nights XXL kebab have had me bursting before now, I tried to hold but was nowhere near civilisation and a cat walk squat was out of the question as cab and trailer were close, so a tree near a farmers field was fertilised.
Sometimes needs must and that’s why we carry baby wipes etc. I also have a portable toilet roll . Fits in a pocket or vehicle ash tray and has saved me many a time when t’roll runs out
I think we all must have been caught short at some stage, i drove tippers for a while years ago we used to get in the back loaded or empty and get in a corner of the body … cover it up like a cat… sounds crude but its better than craping yourself, i know lots of artic drivers that have got under the trailor me included…not good but needs be sometimes.
duck-down:
You guys that are lucky enough to use an RDC toilet (grubby and revolting as they might be) may not need to respond as all your needs are catered for.
Others that are hardier and made of sterner stock may just know the answer.
When parked up for the night in a lay-by or other such place, how do you guys have a dump when there are no loos about?
Squat by the wheel and hope nobody strolls/drives by?
Take a folding frame with a bog-seat and dog-poop-bag attachment and cover yourself with a poncho for some privacy?
Find or dig a suitable rabbit hole?
Clench your bum sphincter and â– â– â– â– muscles 'till you reach civilisation or MRSA?
Or another solution?
I ■■■■in the bog at home mate - wouldn’t do a night out if you paid me… 
Axle spread.
I asked some of the guys at work this question and the best reply was;
One of the drivers emptied his cool box of food, lined it with bin bags, has his emergency dump, wrapped up the bag for disposal later and re-stocked his food back in the cool box.
He was on a truck breakdown in deep snow at minus something silly outside.
Cool. The food made its journey from the coolbox, in and out of the driver, and back into the box.
exit:
Cool. The food made its journey from the coolbox, in and out of the driver, and back into the box.
Lol 
I always stop off somewhere for a dump before I park up if I’m going to be nowhere near a toilet. Never been caught short yet. Some people need to control the back eye I reckon!
I suppose we all know about the tipper man who got into the box then a bus full of Nuns ,brownies or school girls pulled up along side?
Squat on cat walk and put a bag under and jobs done
Was in austria one night and was properly busting for crap, the only option was to go a take a â– â– â– â– round the back of a building, it was a spar shop if i remember rightly, luckly it was pretty much a ghosty so required only one sheet.