Intex, if you type "cycle helmets" into Google you will soon find plenty of advice regarding them, but, as cycle helmets are
designed to provide protection only in falls where
no other vehicle is involved, I doubt if much of it will reassure you: the only certain way to avoid head injury is to get off your bike, stay at home, and be careful you neither fall out of bed or down the stairs. And do not think you will be any safer travelling by car or walking: the incidence of head injuries within these travel modes is just as high.
The problem is that motor vehicles are very dangerous. Unfortunately their new owners, styling them innocuously as "horseless carriages", managed to gradually insinuate them on to our public highways, and our forebears were then unable to relegate them to separate "ways" as they had wisely done a century earlier with the railways. Even their puny attempt to restrict speeds with the red flag men was soon derided, the new motor vehicles being in the hands of the rich and the powerful. If you read some Edwardian novels such as E M Forster's, Howards End, you will find already references to "road hogs", and collisions, all the perpetrators being "upper class".
Here is a brief selection of sites which may be of help:
Peter Clinch's Packs Page 2
Cycle Helmets: an international resource
Cyclecraft