Four hour journey - how do I manage a loo stop?

[EmmaGrundyForPM]

I am making a four hour journey to pick up my mum on just before Christmas. Dog was due to stay behind with dh but now dh might need to go to the office so am considering taking dog with me.

Dog loves the car and travelling so will easily cope with the journey as long as I stop to let him out to pee and stretch his legs at some point. But what do I do about peeing and stretching my legs????

Normally, journey is on motorways and I stop at a service station to use the loo and grab a coffee. But I can't take the dog into a service station. Do I just leave him.in the car and be as quick as I can?

What do other people do in this situation? He's never been left at home for more than a couple of hours so I don't want to leave him all day with a neighbour popping in to let him out a couple of times.

I frequently do 7 hour journeys with my dog. I have left my dog in the car, but last time I did a long journey with her ( the last 4 hours on A & B roads) I was desperate for the loo and knew nothing was nearby so I drove up a very small side road, stopped in a gateway and weeed behind the car. In the past I’ve stopped at garden centres where she is welcome in the cafe, at pubs and at supermarkets.I’ve never actually taken her into a loo with me, she waits in the car!

I regularly travel alone a 6 plus hours mostly on the motorway. I always stop at service stations. The dog is in a cage in the boot of my SUV and I usually park near the entrance and where possible I back into a space so that the boot is against a hedgerow or similar (I know every bloody service station on the motorway, cafe parking loos whether or not you've got to cross over the motorway to get a drink) so no one can walk by look in and see the dog and/or close to other cars with people in them (electric charging points are good). I usually go for a pee myself first so as not to publicise the fact that there is a dog in the car and then walk him. The car is alarmed and frankly it's not that obvious to the casual observer that he's there. I see lots of people doing the same thing and I'm not constantly reading about dogs stolen from cars in motorway service stations. In fact I googled it and couldn't find anything just people raising concerns that it might happen.
Our local Facebook page has over the last few years detailed a couple dogs that have been stolen from cars but they were on both occasions parked outside a village shop I suspect the owners hadn't locked the car.