The offence relates to section 22 of the RTA
An Act to consolidate certain enactments relating to road traffic with amendments to give effect to recommendations of the Law Commission and the Scottish Law Commission.
If a person in charge of a vehicle causes or permits the vehicle or a trailer drawn by it to remain at rest on a road in such a position or in such condition or in such circumstances as to involve a danger of injury to other persons using the road, he is guilty of an offence.
It covers things like parking on a blind bend or approach to a humpback bridge or right on a junction so that traffic has to risk a head on collision to pass because their visibility is blocked- by the car itself or the road layout and the car forces traffic into a potentially dangerous overtaking manoeuvre, or blocking the pavement so pedestrians (e.g. pushchair & wheelchair users) have to step into the road to pass.
The prosecution has to prove that:
(1) You left it there (hence the S172)
(2) The position/condition that it was left caused a danger of injury to others using the road.
(The "in such condition" part would cover not applying the handbrake so that the vehicle could roll, having something unmarked sticking out a long way, or a severe oil/fuel leak spreading out over the road)
I'm unclear on (2) whether a photo of the position would do, or whether they have to observe someone risking injury.
The FPN is £100 + 3 points.
A defence would be "circumstances beyond your control" like a breakdown that locked the transmission so it couldn't be moved until recovery arrive.