N/C as could be outable.
I live on a very busy road. The layout is such that I step out of my front door (mid very long terrace) onto the pavement, then the road (single track) with cars parked down the length of the far side of the road, then a stone wall. So basically you cannot get into your car on one side because it is flush to the wall. no other options to park.
My car has sliding doors plus is a people carrier, so I have a seat removed by the door on the 'road side' of the car so we can all climb in from the one side and I can strap all DC in (I have 4 under 6) while stood in the car.
My car is in the garage so I am borrowing my mum's car for the trip I needed to do today with the younger 3 DC (eldest at school) which is a regular 5 seater. She has 5 point harness seats for DC2 and DC3 already strapped into the car, one in the middle and one on the road side. these seats are a complete pain to fit so they stay in permanently as DM drives DC2 and DC3 to their swim class so it's logical to have them 'roadside'. Car was parked one house down from me.
So today I strapped DC4 (10 weeks) into their car seat and left them in my hallway with the front door open while I put DC2 and DC3 into the car. I then locked DC4 in the house, drove the car to the bottom of the road (about 10 houses down), turned the car in the turning space and parked up on the pavement outside my house (this is standard practise on my road for offloading stuff because of the parking situation so as not to block traffic, the pavement is wide enough for a car to fully park on it) to load DC4 into the car.
The neighbours from a few houses down happened to be on the street and saw what I did and gave me a lecture about how irresponsible I was to leave the baby in the house alone and 'drive off' (note, they had seen the whole episode so it was clear what I was doing and why).
Now to my mind I did the most sensible thing - I couldn't physically get DC4's car seat in with the car parked because of the wall. If I had reparked the car far enough from the wall to open the door enough to get the seat in I would have blocked traffic. DC4 was safely strapped into a car seat in the house (no dogs or other pets or other children in the house). I was 'gone' less than 2 minutes, probably more like 1 minute.
So WIBU to leave DC4 in this situation? as a one off as it's not my usual car? I didn't even think 'should I? shouldn't I?' - it seemed obvious to me!
Sorry its long, trying to give a full picture of the layout etc so as not to dripfeed!!