Insecurity..

A couple of years back a college senior whom I silently admired as my mentor and looked forward to learning a lot of lessons from him died in a street accident.As the story went he tried to cross a busy railway line unaware of the fact that a train was approaching.He ended up dead and I was left shell-shocked
Even in his death I learnt a lesson of not crossing a busy street or a junction without being aware of the consequences that lay ahead.That is to make myself sure that the street is perfectly safe to be crossed.Today while returning from office I thought of a old primary school science lesson which instructed us to look at both sides of the road before crossing the road.Now according to the instruction which I vividly remember we have to look at our right first,then left and then right again.And I was left wondering that why we should be looking at the right for the second time.This is a question that I never asked my primary school science teacher but I was forever left wondering as a consequence.
If the answer is an ambiguous one I would love to ask the replier that why should we not look at the left again after right,then right,then left and be stuck at the same place forever.
Was that a trick our teachers played out so that before we come to a conclusion the green signal flashed before us to cross the road..
I am still confused..