Date: 202111
Local time of day: 0601-1200
Location: EWR.Airport, NJ
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ground EWR
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Human factors: Fatigue; Confusion; Situational Awareness
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Deviation / Discrepancy - Procedural Clearance; Ground Incursion Taxiway
Detector: Person Air Traffic Control
When detected: Taxi
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Airport; Chart Or Publication; Weather
Primary problem: Chart Or Publication

Narrative: During brief at gate in EWR I mentioned to First Officer EWR had some tricky taxiways and whole area here is a 'HOTSPOT'. Conditions; Wet; Rainy; Overcast; they said 10 miles on ATIS but it was hazy. Taxiing out from abeam gate XX. We rolled forward to the north. First Officer and I saw the sign for RC taxiway and I turned right. Ground gave us taxi instructions; 'Aircraft X; RC; Bravo; Romeo; Runway 22R at Whiskey'. Ground then said (as we taxied east out of ramp) that he'd appreciate it if we didn't use A9 in the future as it was a ramp entry not exit. (There were no other aircraft taxiing around us.)  We inadvertently were not on RC but on A9 taxiway!  The signage somewhat misled both of us seeing the RC sign on our immediate left.  (A9 sign must have been on our right) those taxiways are close together and simple and easy mistake to make. I realized we were on A9 at this point because it didn't go straight thru to Bravo only Alpha then ended.  First Officer and I were confused for a few seconds and I realized RC taxiway was in fact on our left! We should have stayed north on ramp for the next right turn. If you are viewing the EWR 10-9 you can see this area of uniqueness; you must continue north and west to get to RC. So we turned left on Alpha joined RC then Bravo and continued cleared taxi route. Established on taxiway Bravo I then immediately apologized to Ground Control and said the signage was a little misleading at 'that' intersection.  I understand our error completely.   But First Officer said 'I don't get it we are on RC!' I said no we were not. Also the taxiways were hard to see painted nomenclature with wet and reflective surfaces.  Was flying a 5 day sequence that had us up very late on west coast first three nights then sequence had us leave early on east coast on day 5. Better to construct sequences the opposite way. An early getup followed by next several day's late departures is taking the 'human element' into consideration! This may have been a casual factor if you look into our sequence.  Unfortunately; this human element in regards to sleep patterns has disappeared!


Second narrative: During our departure briefing; the Captain said that there were some confusing taxiway and stated that the entire airport is a hotspot. When taxing out of ramp area; Ground stated 'RC B Runway 22R'.  Once crossing A to B the controller stated that we used A9 not RC.  We both agreed and saw the signage for RC; but based on the taxi plate; the Captain did turn early. Five day sequence with late start and backing earlier each day and in which we ended last day with a XA:00 wake up; but previous days on West Coast; so overall sequence fatigue.  We briefed what was expected; but both missed; and I think human factors did come into play.  Lead out/in lines drop you off at A9; maybe RC on deck with arrow forward would keep this from happening; also that part of the ramp is uncontrolled; maybe fixing whatever reason its uncontrolled would help.


Synopsis: Air carrier flight crew reported they turned on to the wrong taxiway at EWR Airport and cited confusing taxiway signage and fatigue as contributing factors.