Passive: Please, help that blind man cross the road.

Active : [[1]]

 

 

In this sentence, the passive of the sentence expresses ‘request’.

Expresses ‘request’ in the Active Voice is : Verb1 + Object is used. But, 

there is the usage of ‘please’, ‘kindly’, ( used in the beginning or at the end of the sentence).

We constructed will be – 

You are requested to + Verb1 + Object.

So, the answer is "You are requested to help that blind man cross the road".