Is the sentence correct?

“this morning” may not be needed. The 9 am ( or 9am) explains the time.

Thanks, Punkey.

If we removed "this morning", the sentence would read as follows:
The traffic accident occurred at 9am. (It no longer indicates when it happened besides the time: this morning, this afternoon, this evening, yesterday, etc.)

That’s why I said “may “ not be needed.

Context would help.