There were not very many people in the road, because it was early in the morning. I’m almost sure that is also correct to say “There were not really many people in the road …”. Could confirm what I think? If the answer is yes, would the meaning be the same?
Yes, it is correct. The meanings are similar. All other things being equal, the version with “very” seems more factual and objective. The version with “really” may have additional context-specific connotations, to do with people’s desires or expectations for example.
‘On the road’ is the phrase that I would have preferred to see used in the original sentence.
There were not many people on the road - there wasn’t much traffic and there weren’t many pedestrians.
There were not many people in the road - there weren’t many people standing or walking in the middle of the road.