abaddon
Penultimate Amazing
Extremely poor analogy. If the policeman 'waved you through', that becomes part of your defence in mitigation. However, you won't get far as even if 'a policeman waves you through', you are still expected to use your own eyes and judgement when driving.
In the UK part of driving theory (or at least it was when I took my driving test) is that you should never 'wave people across the road', especially young children, as you may be putting them in danger.
It's all very well motorists waving their hands and blinking and flashing at each other, but you ultimately are responsible to ensure you drive safely.
That is comprehensively wrong.
UK highway code
105
You MUST obey signals given by police officers, traffic officers, traffic wardens (download ‘Signals by authorised persons’) and signs used by school crossing patrols.
And as for road courtesy? I hope to never encounter you on the roads.
