The 26-year old striker will join the Hibees for the remainder of the season just six months after penning a two-year deal with County.
Since departing Ashton Gate in 2011, the former England U19 international has played for Barnsley and Charlton Athletic prior to his move to Meadow Lanein July 2013.
Haynes posted the following on Twitter:
Now on route 2 Scotland. Off on loan 2 Hibs 4 the rest of the season! #spl
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