Question

The police shouldn’t allow people to park there. In passive voice

Answer 1

People shouldn't be allowed to park there by the police.

Explanation

It was a modal active verb case. Modal verbs are words such as can, could, may, might, would, should, etc. When we convert a modal active into passive, we use ‘be’ + Past Participle. The rest of the rules are the same.  

Things to remember:

1. An interrogative active will remain interrogative in passive.